„The Sculptured Proteins series on CellGod.live began with Artemis of Ephesus, who turned out to be the 26S proteasome — the protein-recycling machine hidden inside a cylindrical statue. Then came more: the coat of arms of Trier (casein kinase CK1α), the Warsaw Mermaid (the Gs heterotrimer, PDB 6eg8), the sacred swastika of Bali and Tibet (the purine-synthesis enzyme PAICS), Hermes of Naples (the chemokine MCP-1/CCL2, PDB 1don) and the busts from the gardens of Wilanów (deubiquitinating enzymes, such as UCH37, PDB 3ihr). In kindred series we also decoded insignia and wardrobe — from the Romanov double-headed eagle to the crinoline corset.”
This time, the figure of Hercules awaits discovery.
1. The Farnese Hercules
This is no ordinary statue. It is a colossus — a marble giant 317 cm tall (without the plinth), standing in the Great Hall of the National Archaeological Museum in Naples. The sculptor signed it at the base: Glykon. According to that signature, he made it as a copy of a lost original by Lysippos from around 320 BC, but in reality it was carved around 216 AD, in the reign of Emperor Caracalla, and stood in his baths in Rome. It lay in the rubble of the Baths for over thirteen hundred years before Cardinal Alessandro Farnese had it excavated in 1546. Remember that word — „Baths.”
Glykon rendered Hercules in a classic contrapposto: the body’s weight rests on the right leg, the left is slightly bent. The torso twists to the left, the head is bowed, the gaze directed downward — as if the hero were resting after his twelve labours. His right hand is clenched behind his back, hiding the golden apples of the Hesperides. His left arm leans on a pillar draped with the skin of the Nemean lion — the beast he slew in his first labour. The pillar rises from a base against which his club rests. The muscles are exaggerated to the limits of anatomy: every edge of the ribcage, every groove between the ribs, every fold of skin on the abdomen is carved with surgical precision. The beard and hair are curly, dense, almost alive.
In the photograph taken on 6 November 2022 by Birute Vijeikiene, source Shutterstock, tourists circle the statue. They stand at its feet, raise their phones, small as children at a giant’s feet. The photo does not lie about the scale: the Farnese Hercules is not a sculpture to be viewed up close. It is an architecture of the body, designed to overwhelm with physical presence.
Did Glykon know that he had carved the greatest regulatory machine of the cell — the complex that decides which genes live and which die?
2. The Protein — the Mediator Complex (PDB: 8TQW)
What is the Mediator?
In the nucleus of every one of your cells lies a library of some twenty thousand volumes — your genes. But a library does not read itself. The reader is an enzyme called RNA polymerase II (Pol II) — the machine that transcribes genes from DNA into RNA. Pol II, however, has a problem: it is like a perfect printer with no operator. It does not know which volume to open, when to open it, or how many copies to print.
That operator is the Mediator. One of the largest protein machines in the nucleus: built from about thirty different proteins, standing roughly 46 nanometres tall (460 ångströms; one ångström is a tenth of a nanometre — about the width of an atom). The Mediator works like the genome’s interpreter: on one side it listens to reports from transcription factors — scout proteins that recognize specific DNA sequences and report: „now we read the insulin gene,” „now the muscle-building gene.” On the other side, it connects to Pol II and helps it take its seat precisely at the start of the right gene. The two parties speak different languages — the Mediator translates. It decides which genes live and which stay silent. Without it, no complex organism — from yeast to human — could govern its genes.
On this blog, RNA Polymerase I has already been discovered in the Ark of the Covenant, and RNA Polymerase II in the figure of the Mother of Jesus Christ. The Mediator — the intermediary between them and the genes — was still waiting for its figure.
The discovery of the Mediator began in 1990 in yeast, in the laboratory of Roger Kornberg (Nobel laureate of 2006 for studies of the transcription machinery); the complex itself was purified and named in 1994 (Kim et al., Cell). Since then we have known the complex is evolutionarily conserved — the yeast and human Mediators are the same machine in different sizes.
What is structure 8TQW?
8TQW is a code in the Protein Data Bank (PDB — the world’s public, free archive of protein structures). The entry’s full name: Structure of human transcriptional Mediator complex — the complete human Mediator with its kinase module attached. The structure was solved by cryo-electron microscopy (cryo-EM) — a technique in which molecules are flash-frozen in a thin film of ice, photographed millions of times under an electron microscope, and a computer assembles the images into a three-dimensional model. It is like rebuilding a statue from millions of photos taken at random angles in fog.
A few numbers:
29 distinct proteins in a single complex,
dimensions of roughly 460 × 210 × 160 ångströms — a vertical giant on the molecular scale,
resolution: 8.2 Å for the whole, refined to 4.7 Å for the core and 6.7 Å for the kinase module (at that resolution you can see the coils of a protein helix — the way you see planks in a wall, though not yet the nails).
The structure comes from the team of Kuen-Lin Tsai (the University of Texas Health Science Center at Houston), in collaboration with Kenji Murakami and Thomas Boyer, among others; the first authors are Szu-Fan Chen and Ti-Chun Chao. The results were published in October 2024 in the prestigious journal Molecular Cell (DOI: 10.1016/j.molcel.2024.09.001). The PDB entry was deposited in August 2023 and released on 9 October 2024. It is the first near-atomic structure of the complete human Mediator — until then, researchers had seen only its fragments or blurred silhouettes.
Structure 8TQW is not a single, continuous map. It is a composite image: two independently refined fragments — cMED-HookΔ at 4.7 Å and CKM-Hook at 6.7 Å — were merged into one model. Hence the „seam” visible in some Mol* renders: the boundary between the body and the kinase module is not fully atomic, but architecturally faithful.
Two subunits are absent from this structure: MED26 (metazoan-specific, required for SEC recruitment and full transcriptional activation) and CDK19 (a paralogue of CDK8 that can substitute for CDK8 in certain tissues). Their absence is not a preparative error — it is a functional state. A Mediator lacking MED26 and wearing the CKM is a Mediator in repression: standing, but not walking.
How is the Mediator built?
[IMAGE: 8TQW in Mol* cartoon view — general view of the whole complex]
The Mediator consists of two parts that can detach from each other — and the entire meaning of this machine lies in that detachment.
Part one: the body of the hero — structure 8TRH. The Mediator core (cMED), built of three modules that scientists named… anatomically: the Head (seven proteins), the Middle and the Tail. We are not joking — in the first, blurry microscopic reconstructions the Mediator really did look like a figure, and the names stuck. The Tail catches signals from transcription factors, the Middle processes them, and the Head connects to Pol II — this is where the gene-reader lands. The whole is clasped by subunit 14 — a long scaffolding protein running the core’s full length.
A warning, because it is easy to get lost here — there are two heads. The Head module is seven proteins that in 8TQW lie within the body, not at the top. The statue’s head — the very top of the silhouette — is three Tail subunits: 16, 23 and 24. Looking in Mol* at the top of the complex, you see exactly them. In section 3 we decode the sculpture by this second geography.
Part two: the plinth — structure 8TQC. The removable kinase module (CKM). Four proteins: CDK8 (a kinase — a stamp-enzyme that presses phosphate groups onto other proteins, changing how they work), cyclin C (CCNC) — the ignition key of CDK8, and two giants: subunits 12 and 13 (over 2,000 amino acids each). The plinth (8TQC) is a removable brake: when it clamps onto the body (8TRH) at the site called the Hook, the Mediator stops admitting Pol II and the genes fall silent. When the plinth detaches, transcription starts.
The complete giant: structure 8TQW = body (8TRH) + plinth (8TQC) together. The Mediator in its silenced state, with the brake attached.
One thing is worth noting: structure 8TQW shows the Mediator in solitude — no polymerase II, no activators, no DNA. The machine’s most important partners remain outside the frame.
More details in the decoding sections — that is where the real story begins.
3. Decoding — Level 1: The Silhouette
Before we begin comparing — one caveat. Proteins do not have arms, legs, heads or plinths. Ancient sculptors encoded a three-dimensional molecular structure in a form recognisable to humans — the human body. This is an approximation, not a 1:1 copy. The sculptor had to „stretch” the protein structure onto the silhouette of a hero — assigning protein domains to head, torso, limbs and props. In some places the match is almost perfect (curls = α-helices); in others the seam shows. The code is approximate, not literal — but consistent.
[IMAGE: Statue of Heracles, Farnese Hercules. Roman marble statue, copy of original by Lysippos. Isolated with clipping path, Dima Moroz – Shutterstock. beside structure 8TQW in Mol* surface view]
Let us stand the statue and the protein side by side. In Mol* you can display a protein as a compact solid — the so-called surface — instead of a tangle of ribbons. Then you see shape, not innards.
Look closely: every element of the sculptural group — the lion’s skin, the club, the stand, the plinth — is not decoration. These are elements that, once separated, reveal protein folding: the way an amino-acid chain coils into a three-dimensional structure. Glykon did not carve a hero with props — he carved a machine with its domains.
What you see on the statue and what it encodes
317 centimetres of marble correspond to 46 nanometres and 29 proteins — one of the largest regulatory complexes of the cell nucleus.
Head and shoulders — curly locks, a bowed brow, a powerful neck. This is the top of the Mediator complex — three proteins (MED16, MED23, MED24) that receive signals from gene activators.
Torso — a massive chest, abdomen, hips. This is the axis of the entire machine — twelve proteins forming the core of the complex, with MED14 as the „spine” running its full length.
Stand — the element the hero leans on. This is the lower part of the core with the Hook — the site where the kinase module attaches to the Mediator.
Club — a long, rigid shaft that also serves as a prop. This is the elongated protein MED21, which together with MED7 forms the Hinge — the place where the whole machine can bend.
Lion’s skin — the trophy of the first labour, draped over the stand. This is protein MED4, which connects different parts of the complex.
Lion’s head — the muzzle and mane at the top of the stand. This is MED1 — the largest protein of the Mediator (1,581 amino acids), which recognizes gene activators.
Legs — the right bearing the weight, the left slightly bent in contrapposto. These are the lower proteins of the core — the zone where the body of the hero (8TRH) ends and the plinth (8TQC) begins. In the protein structure a gap is visible between these two bodies — the region between MED13 and MED6, which is not fully resolved in cryo-EM. On the statue this same region has its own history: the original legs of Hercules were lost, Guglielmo della Porta sculpted replacements, and the originals were not restored until 1787. The region that was physically discontinuous in the ruins is structurally discontinuous in the protein.
The plinth = the removable brake
The marble plinth is not part of the silhouette — the statue stands on it, but the sculptor carved it as a separate body. The kinase module CKM works exactly so: the English term dissociable module means literally „a detachable module.” The cell attaches it to the Mediator when a gene must fall silent, and detaches it when the gene must speak. The statue in Naples shows Hercules at rest, after the twelve labours — and the complete complex 8TQW shows the Mediator in the silenced state, wearing the CKM. Both depict the giant at rest.
One caveat regarding proportions: structure 8TQC shows the CKM as a body considerably more elongated than the marble plinth, which is relatively compact. It must be remembered, however, that the statue was excavated in fragments — the torso from the Baths, the head from a well in Trastevere, the legs found separately. Guglielmo della Porta sculpted replacement legs, a left forearm with the apples (plaster), the club and the fingers of the left hand. Given this scale of damage, the plinth may well have been incomplete — and its present proportions may not reflect Glykon’s original.
The Apples of the Hesperides
From the front, Hercules is a smooth, compact mass — a marble surface without cracks. From behind, the same — smooth back, solid stone. But in one place, hidden behind his back, in a clenched fist, the sculptor revealed what the entire statue is made of: round bodies, pressed together in a hand.
[IMAGE: Apples Farnese Hercules, Uffizi Gallery, Ivan Moreno sl – Shutterstock. Close-up from Mol* — MED18 in cartoon and ball-and-stick view: helices as spirals, a loop as a tube, ball-atoms at its end; this is exactly the spot of the fist holding the apples of the Hesperides]
This is exactly how structure 8TQW works in Mol*. In surface view, the protein looks like a statue: a smooth, impenetrable surface. Switch to spacefill — and beneath the surface, the spheres of atoms appear, the building blocks of the entire complex. The apples of the Hesperides are precisely this moment of switching: Glykon hid behind the giant’s back, in his hand, a glimpse of the atomic level of a structure that from the front looks like a solid mass.
The MED18 region lies exactly where that fist is. The entire Mediator is built of atoms — but only here did the sculptor let you see them.
4. Decoding — Level 2: Close-up
[IMAGE: two close-ups from the statue — Hercules’ head in curls and the lion’s head on the stand — beside the corresponding fragments of 8TQW in cartoon view (dense bundles of α-helices: subunits 23, 24 and 1), the rest of the complex greyed out]
Level one showed the whole silhouette. Now we zoom in — on two heads: the hero’s and the lion’s. At this magnification the cartoon view shows the protein in the script of its inner architecture: spiral ribbons are α-helices — the most common protein motif, a spring made of amino acids; flat arrows are β-sheets, and thin cords are loops.
And here an observation awaits that changes the reading of the whole sculpture. The head of Hercules — subunits 23 and 24 — and the head of the lion — subunit 1 — are, in structure 8TQW, places of an exceptional density of α-helices. Coil upon coil, spiral upon spiral: dense bundles of twisted ribbons. And on the statue? Exactly these two places Glykon covered with the densest, most carefully carved curls: the hero’s mop and beard, the lion’s mane and muzzle. A lock of Hercules looks like an α-helix in cartoon view — the same rhythm, the same coil, the same ordered chaos.
Coincidence? Consider the chisel work. A smooth hairstyle takes a few strokes; a curl takes dozens of blows and hours of labour. The beard and hair are the most labour-intensive texture of the entire statue — the sculptor invested more in them than in the chest muscles. No one spends such effort without reason: the curliness here is carved, deliberate. And it covers precisely those proteins that are themselves built of spirals — subunits 23 and 24 are almost pure bundles of helices laid in regular repeats — like curls.
There is one more level of historical irony in this. The spiral ribbon as the symbol of the α-helix is a convention invented in 1981, when Jane Richardson gave proteins their iconic „cartoon” look. Glykon used the same sign — the spiral — in 216 AD.
5. Conclusions
In mythology, Hercules is the embodiment of a single idea: strength placed in the service of order. The twelve labours are not acrobatics — they are the establishing of order where chaos reigned: the stables, the hydra, the boar, the apples guarded at the edge of the world. The Mediator does exactly the same in the genome: it establishes order amid the chaos of twenty thousand genes, deciding what will be read, when, and how loudly. The greatest Greek hero and the greatest regulator of the cell share one identity: the giant who decides.
This giant sometimes falls ill — and then we fall ill. CDK8 — the kinase sitting at the base of the complex, next to subunit 13 — is an oncoprotein: in colorectal, breast and pancreatic cancers and in leukaemias it is often amplified or overactive, and the first drugs blocking CDK8/19 (such as Senexin B and its successors) are passing through early phases of clinical trials. Subunit 12 — a protein of the plinth zone, one of the anchors of the kinase module — is mutated in about 70% of uterine leiomyomas, the most common tumours of women (a 2011 discovery, Science), while its rare variants cause the developmental disorders known as Ohdo, Lujan–Fryns and FG syndromes. Disruptions of MED13L, the cousin of MED13, cause a syndrome of developmental delay and intellectual disability. When Hercules falls, the order of the entire kingdom falls — of the cell and of the body.
But the Mediator is not doomed to disease. Its function depends on how you live — and science is beginning to document this.
Vitamin D is the first, best-documented factor. Its receptor (VDR) does not work without the Mediator — specifically without subunit MED1 (also known as TRAP220). MED1 is the bridge through which vitamin D „switches on” genes responsible for immunity, keratinocyte differentiation and calcium homeostasis. Without MED1, the vitamin signal is lost on its way to DNA.
Physical exercise changes the Mediator in muscles. After intense training, the gene NURR1 (NR4A2) is upregulated — one of the most strongly induced genes in human muscle. MED13, a subunit of the kinase module, regulates metabolic gene expression in muscle — the Mediator decides whether the muscle „remembers” the effort.
Diet and fatty acids influence the Mediator through the receptor PPARγ (activated, among others, by fatty acids). MED1 is required for a high-fat diet to cause liver steatosis — mice with a liver-specific MED1 knockout fed a 60%-fat diet for four months did not develop fatty liver, while control mice developed severe steatosis (Hepatology, 2011). PPARγ activates lipogenesis genes, but without MED1 it cannot reach the polymerase — the signal „store fat” is lost on its way from receptor to DNA. MED1 is also phosphorylated by AMPK — the cell’s energy sensor, which responds to fasting, exercise and metformin. AMPK places three phosphates on MED1 (Ser656, Ser756, Ser796), changing its activity.
Sleep and the circadian clock are another dimension. The core cellular clock — the heterodimer CLOCK:BMAL1 — recruits the Mediator to initiate transcription of clock genes. Without this connection the clock does not tick. Sleep deprivation, shift work, jet lag — all of these disrupt the BMAL1 rhythm and, through it, the rhythm of the Mediator. The cell loses synchronisation because it loses the synchronisation of its conductor.
And then there is the question we have asked on this blog since the first entry. Glykon moulded in marble a figure with a head, a torso and legs, with a removable covering on a hook, a weapon set down at the ready, a hidden treasure in its fist, and a gaze turned downward — in the year 216 AD. Science reconstructed that same architecture atom by atom in 2024 and named it: the Mediator, the machine that decides which genes live. How did they know?
The greatest hero of mythology has stood in Naples for four hundred and seventy-nine years. The greatest guardian of your genes has stood in every one of your cells forever.
As within, so without.
Before we part with the hero — one wider look. Hercules did not stand in a void: he was excavated in 1546 from the rubble of the Baths of Caracalla, the largest baths of Rome at the time of their opening. Now look at their plan: a regular, almost square outline, a dome at its heart, gardens all around, channels in the walls, vast underground levels beneath. You know this view. It is a cell — and it is no accident that the hero was deposited inside one.
[IMAGE: ROMEWISE – Your go-to guide to Rome]
Appendix: The Baths of Caracalla — an Osteoblast (Bone-Building Cell)
[TITLE IMAGE: bird’s-eye reconstruction of the Baths of Caracalla – Gzen92 – WIKIMEDIACOMMONS]
We cannot be certain of the cell type — but the osteoblast has more in common with the Baths of Caracalla than any other candidate.
Look at the plan of the baths once more. An almost perfect square — exactly the shape of an osteoblast in cross-section (a cuboidal cell). The complex has a clear polarisation: double secretory channels in the front wall (the apical side, facing the bone matrix), and on the opposite side — the entire Golgi pathway set into the membrane. The halls (H) on both sides are set into bulges of the wall itself. The largest baths of their-day Rome are a bone-building cell.
Mapping
[MAPPING IMAGE: plan of the complex with halls labelled A–U — a cell cross-section]
G — Caldarium (the dome) is the cell nucleus — the only spherical structure in the complex; its double wall is the double nuclear envelope.
T — Forni (the furnaces) is the centrosome: the furnaces stand right beside the dome (G) — just as the centrosome hugs the nucleus. And as microtubules grow radially out of the centrosome, the furnaces fed the hypocaust — a network of heating channels beneath the floors. The furnaces are the organising centre of that network; the channels themselves are S.
S — Sotterranei (the underground levels) are the microtubules and cytoskeleton — a network of tunnels roughly 6 metres wide beneath the entire complex (total length estimated at 2–4 km, depending on the source). On the plan, S is visibly connected to T (furnaces/centrosome), U (watermill/integrins), R (Mithraeum) and H (halls/mitochondria) — forming one continuous peripheral system running along the membrane.
B — Giardino (the gardens) is the cytoplasm — the open space surrounding the organelles. The paths visible in the gardens encode the cytoskeletal filaments organising the cell interior.
A — Tabernae (the channels in the wall) are the secretory channels of the apical side — a double network of channels in the front wall through which the osteoblast releases bone matrix proteins (type I collagen, osteocalcin, osteopontin) into the extracellular space. The channels adjoin Via Nova (a bone sinusoid).
D — Cisterne (the cisterns) are the Golgi apparatus — the very same Latin word: the cisternae of the Golgi. The osteoblast has an exceptionally well-developed Golgi for processing and sorting vast quantities of collagen.
E — Stadio is the trans-Golgi network (TGN) — the protein-sorting space.
F — „Biblioteca”* is the secretory vesicle — an enclosed space storing sorted proteins.
C — Scalinata (the corner staircase) is the exocytosis site, membrane fusion — stairs leading outside.
H — Sale (the halls, on both sides) are mitochondria — elongated buildings set into bulges of the wall on both sides of the complex. The osteoblast requires large amounts of energy for collagen synthesis and secretion.
U — Mulino (the watermill) is the integrin complex and focal adhesion — a rotary mechanism in the membrane converting mechanical force into a biochemical signal (mechanotransduction). The osteoblast responds to mechanical loading — this is why bones strengthen under exercise. The watermill converts flow into work — integrins convert force into signal.
R — Mitreo (the Mithraeum) is the trace of the endosymbiotic origin of mitochondria — an underground temple of a foreign eastern god with its own independent cult, its own rituals and hierarchy, hidden in the membrane, adjacent to H (mitochondria). Mithras — a Persian solar deity that settled inside a Roman structure — encodes the ancient bacterial organism that, billions of years ago, was engulfed by a eukaryotic cell and became the mitochondrion. Its own cult = its own mitochondrial DNA (mtDNA). Five interconnected chambers = the remnants of an independent genetic apparatus.
O — Frigidarium is the rough endoplasmic reticulum (RER) — the largest hall, directly beside the nucleus (G). The osteoblast has exceptionally well-developed RER because it produces vast quantities of type I collagen — the most abundant protein of the bone matrix.
N — Piscina is the lumen of the endoplasmic reticulum.
P — Tepidarium is the ERGIC — the intermediate compartment between the endoplasmic reticulum and the Golgi apparatus.
I — Laconicum (the sauna) is the smooth endoplasmic reticulum (SER) — lipid processing.
L — Palestra (the exercise hall) is the protein-folding zone, chaperones.
M — Spogliatoio (the changing room) is post-translational modifications — proteins literally „change their clothes.”
Q — Vestibolo (the vestibule) is the entrance to the ER complex from the cytoplasm.
*The name „Biblioteca” is a modern interpretation by archaeologists, based on niches in the walls — there is no historical evidence that this space served as a library. In the context of the secretory pathway D→E→F→C, this structure encodes a secretory vesicle.
Pathways
[IMAGE: engraving of the interior of the Baths of Caracalla — view from floor level of the frigidarium with arches, columns, coffered ceiling, statues in niches and people on the floor, WIKIMEDIACOMMONS]
The bird’s-eye plan shows the cell as a microscope slide — from above, in cross-section. This engraving
