Talk abstracts

Talk on Saturday 10:30-10:45am submitted by Kristine Potter

A dominant role for polyadenylation in forkhead transcription factor-mediated regulation of a meiotic cyclin gene

Kristine D. Potter (Center for RNA Molecular Biology, Case Western Reserve University), Nicole G. Cremona (Center for RNA Molecular Biology, Case Western Reserve University), Jo Ann Wise (Center for RNA Molecular Biology, Case Western Reserve University)

Abstract:
In the fission yeast Schizosaccharomyces pombe, polyadenylation signals utilized for productive expression of meiotic transcripts during sexual differentiation are bypassed in proliferating cells (1). For the early meiotic crs1 (cyclin regulated by splicing) gene, a bipartite 3' regulatory signal triggers destruction of the nascent transcript (2). Here, we describe a distinct regulatory mechanism for the rem1 gene, which encodes a meiosis-specific cyclin with a later expression window. Proper temporal regulation of rem1 requires positive and negative control of both splicing and 3' RNA processing, which are governed by distinct sequences located upstream from the transcription start site. Although 3' maturation and splicing peak at the same time during meiosis, polyadenylation is still restricted to meiosis when the intron is deleted and is not blocked in mitotic cells by inactivating the 5' splice site. Consistent with the presence of multiple forkhead transcription factor recognition motifs in the 5' control regions, inhibition of rem1 mRNA production in mitotic cells is partially reversed by over-expressing the mei4+ gene, encoding a forkhead protein normally produced only during meiosis, or by deleting fkh2+, encoding a constitutive family member. However, both genetic perturbations are necessary to fully overcome negative control and accumulate rem1 mRNA at levels comparable to those in meiotic cells. These findings, in conjunction with ChIP data demonstrating a nearly identical distribution of Fkh2p and Mei4p across the entire rem1 locus in meiotic cells, support a model in which the two forkhead factors collaborate to promote RNA processing during meiosis. The expression patterns for other middle meiotic genes, including one that lacks introns, are similar to that of rem1, setting the stage for genome-wide studies to comprehensively identify members of the forkhead regulon.

References:
1. Cremona, N., Potter, K. and Wise, J. A. (2011) A meiotic gene regulatory cascade driven by alternative fates for newly synthesized transcripts. Molec. Biol. of the Cell 22, 66-77.
2. McPheeters, D.S., Cremona, N., Sunder, S., Averbeck, N., Chen, H.-M., Leatherwood, J. and Wise, J. A. (2009) A Complex Gene Regulatory Mechanism that Operates at the Nexus of Multiple RNA Processing Decisions. Nat. Struct. Molec. Biol. 16, 255-263.

Keywords: Polyadenylation, Splicing, Transcription factor