Poster abstracts
Poster number 135 submitted by Daniel Totten
hnRNP A1 RNA recognition motifs induce a conformational change upon binding 7SK RNA stem III
Daniel C. Totten (Department of Biological Sciences, University of Pittsburgh), Andrea J. Berman (Department of Biological Sciences, University of Pittsburgh)
Abstract:
Tight regulation of transcription is necessary for cellular survival, homeostasis, and development. Promoter-proximal pausing is a higher eukaryotic phenomenon in which RNA polymerase II pauses shortly after initiation, facilitating the induction of elongation upon phosphorylation by positive transcription elongation factor b (P-TEFb). P-TEFb is, in turn, regulated through association with the 7SK RNA (7SK) to form an inhibitory 7SK ribonucleoprotein (RNP) complex1. When P-TEFb dissociates from 7SK, the RNA forms another set of RNPs with various heterogenous nuclear ribonucleoproteins (hnRNPs), such as hnRNP A1. Here we show biochemically that the RNA recognition motifs of hnRNP A1 (UP1) bind to Stem III of 7SK with ~300 nM affinity. We have found that a base-proximal site is critically important for initiating this interaction. UP1 binding causes a conformational rearrangement in Stem III, exposing sites on the opposite side of the stem. Stem III also binds serine-arginine rich splicing factor 2 (SRSF2), a natural splicing antagonist of hnRNP A1, in the 7SK-P-TEFb RNP2. Together with our results, this suggests a possible mechanism by which Stem III assumes a distinct conformation in each of its RNPs, and the conformational changes arising from protein binding may be important for the switch between the 7SK-P-TEFb RNP and the 7SK-hnRNP RNP. Future work will examine the binding of SRSF2 to Stem III as well as the interplay between SRSF2 and UP1 on Stem III.
References:
1. Guo, J. and D.H. Price, RNA polymerase II transcription elongation control. Chem Rev, 2013. 113(11): p. 8583-603.
2. Ji, X., et al, SR Proteins Collaborate with 7SK and Promoter-Associated Nascent RNA to Release Paused Polymerase. Cell, 2013. 153: p. 855-868
Keywords: 7SK RNA, hnRNP A1, SRSF2