Rpb4 and Rpb7: A Sub‐complex Integral to Multi‐subunit RNA Polymerases Performs a Multitude of Functions

Abstract

SummaryRpb4 and Rpb7, are conserved subunits of RNA polymerase II that play important roles in stress responses such as growth at extreme temperatures, recovery from stationary phase, sporulation and pseudohyphal growth. Recent reports have shown that apart from stress response, these proteins also affect a multitude of processes including activated transcription, mRNA export, transcription coupled repair etc. We propose a model that integrates the multifarious roles of this sub-complex. We suggest that these proteins function by modulating interactions of one or more ancillary factors with the polymerase leading to specific transcription of subsets of these genes. Preliminary experimental evidence in support of such a model is discussed. IUBMB Life, 57: 93 -102, 2005

Unstructured N Terminus of the RNA Polymerase II Subunit Rpb4 Contributes to the Interaction of Rpb4·Rpb7 Subcomplex with the Core RNA Polymerase II of Saccharomyces cerevisiae

“…The Rpb4⅐Rbp7 subcomplex in the 12-subunit RNA Pol II is located very close to the flexible linker connecting the highly conserved C-terminal domain of Rpb1. Although the C-terminal domain is known to play a crucial role in transcription, the Rpb4⅐Rbp7 subcomplex has been shown to affect recruitment of C-terminal domain modifying proteins such as Fcp1 and Ess1 (4).…”

“…Rpb4 and Rpb7 form a subcomplex within the polymerase that dissociates easily under mild denaturing or nondenaturing conditions and shows variable association with the polymerase at different growth stages, leading to the suggestion that the subcomplex could be analogous to the subunit of the bacterial RNA polymerase (1)(2)(3). Whether such a regulatory role can be ascribed to the subcomplex has been a matter of some debate, but the phenotypes of the deletion mutants and the interactions mediated by these subunits suggest that they might have some regulatory role in stress response and transcription (4).…”

“…However, rpb4⌬ strains are temperature-sensitive and cold-sensitive, show poor recovery from stationary phase, are defective in sporulation (a response to severe nutritional starvation), and are predisposed to pseudohyphae formation (a response to mild nutritional starvation) (4). Apart from its roles in stress response, Rpb4 is involved in transcription under moderate and extreme temperatures (6).…”

“…In most eukaryotes, the 12-subunit RNA polymerase II (Pol II) 4 is thought to have little or no influence on the regulation of transcription. Rpb4 and Rpb7 form a subcomplex within the polymerase that dissociates easily under mild denaturing or nondenaturing conditions and shows variable association with the polymerase at different growth stages, leading to the suggestion that the subcomplex could be analogous to the subunit of the bacterial RNA polymerase (1)(2)(3).…”

Multisubunit DNA-Dependent RNA Polymerases from Vaccinia Virus and Other Nucleocytoplasmic Large-DNA Viruses: Impressions from the Age of Structure

“…While bacterial MSDDRP has just 4 distinct subunits, named ␣ (two copies), ␤, ␤=, and , S. cerevisiae pol II has either 10 or 12. While the 10-subunit core enzyme comprising subunits Rpb1, -2, -3, -5, -6, and -8 to -12 is competent in transcription elongation, two additional, dissociable subunits, the Rpb4/7 heterodimer, are conditionally required for transcription initiation (39). Other eukaryotes always have the 12-subunit form.…”