Yeast screens identify the RNA polymerase II CTD and SPT5 as relevant targets of BRCA1 interaction.


BRCA1 has been implicated in numerous DNA repair pathways that maintain genome integrity, however the function responsible for its tumor suppressor activity in breast cancer remains obscure. To identify the most highly conserved of the many BRCA1 functions, we screened the evolutionarily distant eukaryote Saccharomyces cerevisiae for mutants that suppressed the G1 checkpoint arrest and lethality induced following heterologous BRCA1 expression. A genome-wide screen in the diploid deletion collection combined with a screen of ionizing radiation sensitive gene deletions identified mutants that permit growth in the presence of BRCA1. These genes delineate a metabolic mRNA pathway that temporally links transcription elongation (SPT4, SPT5, CTK1, DEF1) to nucleopore-mediated mRNA export (ASM4, MLP1, MLP2, NUP2, NUP53, NUP120, NUP133, NUP170, NUP188, POM34) and cytoplasmic mRNA decay at P-bodies (CCR4, DHH1). Strikingly, BRCA1 interacted with the phosphorylated RNA polymerase II (RNAPII) carboxy terminal domain (P-CTD), phosphorylated in the pattern specified by the CTDK-I kinase, to induce DEF1-dependent cleavage and accumulation of a RNAPII fragment containing the P-CTD. Significantly, breast cancer associated BRCT domain defects in BRCA1 that suppressed P-CTD cleavage and lethality in yeast also suppressed the physical interaction of BRCA1 with human SPT5 in breast epithelial cells, thus confirming SPT5 as a relevant target of BRCA1 interaction. Furthermore, enhanced P-CTD cleavage was observed in both yeast and human breast cells following UV-irradiation indicating a conserved eukaryotic damage response. Moreover, P-CTD cleavage in breast epithelial cells was BRCA1-dependent since damage-induced P-CTD cleavage was only observed in the mutant BRCA1 cell line HCC1937 following ectopic expression of wild type BRCA1. Finally, BRCA1, SPT5 and hyperphosphorylated RPB1 form a complex that was rapidly degraded following MMS treatment in wild type but not BRCA1 mutant breast cells. These results extend the mechanistic links between BRCA1 and transcriptional consequences in response to DNA damage and suggest an important role for RNAPII P-CTD cleavage in BRCA1-mediated cancer suppression.





Published Version (Please cite this version)


Publication Info

Bennett, Craig B, Tammy J Westmoreland, Carmel S Verrier, Carrie AB Blanchette, Tiffany L Sabin, Hemali P Phatnani, Yuliya V Mishina, Gudrun Huper, et al. (2008). Yeast screens identify the RNA polymerase II CTD and SPT5 as relevant targets of BRCA1 interaction. PLoS One, 3(1). p. e1448. 10.1371/journal.pone.0001448 Retrieved from

This is constructed from limited available data and may be imprecise. To cite this article, please review & use the official citation provided by the journal.



Arno Lee Greenleaf

Professor Emeritus of Biochemistry

      My laboratory studies the mechanisms by which different activities in the cell nucleus are connected to the transcription machinery via interactions with the hyper-phosphorylated C-terminal repeat domain (PCTD) of elongating RNA polymerase II. Differential phosphorylation of the CTD, as the RNAP proceeds through successive stages of transcription, orchestrates sequential recruitment of factors to the transcriptase; this serves to coordinate RNA processing events and mRNA nuclear export with gene transcription. To gain a thorough understanding of relevant phosphorylation events on the PCTD, we identified the principal elongation-phase CTD kinase activities in three different eukaryotes, yeast (yCtk1), Drosophila (dCDK12) and humans (hCDK12 & 13).  In addition, we described a novel set of phosphoCTD-associating proteins (“PCAPs”) that we now are investigating primarily in human cells. Our results revealed novel roles for elongating RNAPII, and they engendered several totally new lines of investigation.         

      Recently hCDK12 was shown to be a tumor suppressor for ovarian cancer, and our investigations of this kinase will illuminate its features that, when mutated, can lead to ovarian cancer.

      In another cancer-related project, we are identifying drug targets for a new class of drugs to be aimed at ovarian and breast cancers.

Unless otherwise indicated, scholarly articles published by Duke faculty members are made available here with a CC-BY-NC (Creative Commons Attribution Non-Commercial) license, as enabled by the Duke Open Access Policy. If you wish to use the materials in ways not already permitted under CC-BY-NC, please consult the copyright owner. Other materials are made available here through the author’s grant of a non-exclusive license to make their work openly accessible.