Scientists at the Institute of Organic Chemistry and Biochemistry (IOCB) Prague have, for the first time, revealed the atomic-level details of how cells initiate gene transcription using a stress response mechanism. Researchers, led by Hana Cahová, detailed how RNA polymerase generates RNA with an “alarmone cap” – a protective modification triggered by cellular stress, such as nutrient deprivation or temperature shock – directly at the start of genetic information transfer. This breakthrough, published in Nature Chemical Biology, utilized cutting-edge cryogenic electron microscopy to visualize dinucleoside polyphosphates binding within the enzyme’s active site. “We’re describing something that truly occurs in cells and that we’re now able to observe directly at the level of individual molecules,” said Hana Cahová, highlighting the significance of understanding how cells adapt to threatening conditions.
Alarmone Caps Initiate RNA Transcription in Bacteria
Research published in Nature Chemical Biology details how dinucleoside polyphosphates (NpNs) – molecules forming these alarmone caps – can directly kickstart genetic information transfer from DNA to RNA. The team, led by Hana Cahová, observed that these NpNs utilize atypical base pairing while binding within the RNA polymerase enzyme’s active site, a finding supported by detailed cryogenic electron microscopy data. This discovery demonstrates alarmone caps aren’t merely protective measures during cellular stress, but integral to initiating the transcription process itself. Jana Škerlová’s structural analysis pinpointed exactly how NpNs integrate into the enzyme’s core during transcription. Dr.
Tomáš Kouba added, “Cryogenic electron microscopy allows us to freeze biological molecules in a state very close to their natural form and then determine their three-dimensional structure.”
Dinucleoside Polyphosphates Bind Differently to RNA Polymerase
This interaction was visualized at the atomic level using cryogenic electron microscopy (cryo-EM), a technique central to the project and housed within IOCB Prague’s newly opened cryo-EM center. Jana Škerlová’s structural analysis demonstrated precisely how these molecules integrate into the polymerase core, where genetic information is transcribed. This finding illuminates how cells initiate transcription under stress, creating RNA with alarmone caps that protect genetic material. The team observed that this process allows for a deeper understanding of cellular adaptation to threats like nutrient deprivation or temperature shock.
We’re describing something that truly occurs in cells and that we’re now able to observe directly at the level of individual molecules.
Hana Cahová
Cryogenic Electron Microscopy Reveals Molecular Structures
The research, published in Nature Chemical Biology, centers on alarmone caps—modifications to ribonucleic acid (RNA) that emerge during cellular stress—and how they interact with RNA polymerase, the enzyme responsible for transcribing DNA into RNA. This detailed visualization was made possible by IOCB Prague’s recently opened cryo-EM center, equipped with state-of-the-art microscopes. Tomáš Kouba.
