RNA polymerase III mutants in the TFIIFa-like Rpc37p subunit impair transcription termination and RNA 3' end cleavage

Wednesday, October 10, 2012 — Poster Session II
Noon – 2:00 p.m	Natcher Conference Center, Building 45	NICHD	MOLBIO-8

* FARE Award Winner

Authors

• K Rijal
• R. J. Maraia

Abstract

RNA polymerase III (pol III) is a multisubunit enzyme that transcribes noncoding RNAs such as tRNA, 5S rRNA, U6 spliceosomal snRNA, 7SK RNA and others including a subset of microRNAs. Pol III is deregulated in tumorigenesis. Randomly mutagenized libraries of C53 and C37 were created and screened in a strain that reports if the polymerase fails to stop at the terminator and instead reads through. A minority of mutants map to the C37-C53 dimerization domain and exhibit mild phenotypes, whereas the majority have strong phenotypes and map to a short C-terminal tract previously localized in the pol III active center. Quantification of terminator readthrough transcripts suggests as much as 40% terminator readthrough in some of the mutants. We also monitored intron-containing nascent pre-tRNA levels as a reflection of relative transcription rate in vivo. Notably, these mutants and a rpc2-termination mutant do not show decrease in pol III transcription in vivo as would be expected if they were impaired for pol III recycling. These data provide another important new insight, that termination, even from a fast-elongating pol III, involves 3' end shortening or pol III retraction.

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