Talk abstracts

Talk on Saturday 08:40-09:00am submitted by Sapna Varia

Elucidating a role for Btf in pre-mRNA transcription and splicing

Sapna Varia (Biomedical Sciences, Wright State University), Zhihui Deng, Alok Sharma (Biomedical Sciences, Wright State University), Dr.Tom Bubulya (Biological Sciences, Wright State University), Dr.Paula Bubulya (Biological Sciences, Wright State University)

Abstract:
Nuclear speckles are nuclear storage and assembly sites for pre-mRNA processing factors. Btf (Bcl-2-like transcription factor or BCLAF) was identified in a proteomic analysis of purified nuclear speckles and it localized in a unique pattern that resembles transcription sites(1). Our hypothesis is that Btf has a role in the coordination of transcription and co-transcriptional processing of pre-mRNAs. Recently reported cap-dependent association of Btf with in-vitro synthesized affinity purified MS2-AdML-M3 mRNPs is consistent with such a role(2). Additional evidence for Btf in transcription and/or splicing comes from our observations showing that Btf accumulates on a reporter gene locus in situ. Since Btf is enriched on the transcriptionally activated locus, but not on the inactive locus, we hypothesize that Btf is recruited to this locus during gene activation. To test this hypothesis, we are using this reporter locus to compare the timing of Btf recruitment with chromatin decondensation and the accumulation of chromatin remodeling factors, transcription factors and splicing factors.
SR splicing factors are typically targeted to nuclear speckles by RS domains. Although Btf has an arginine-serine-rich (RS) domain, it localizes predominantly around the periphery of nuclear speckles. We have performed deletion analysis to understand the unique Btf localization pattern. We have confirmed that the RS domain of Btf can function as a speckle targeting sequence on its own; however, removal of the Btf RS domain does not significantly change the Btf localization pattern. This suggests that Btf localization may be regulated differently than other speckle proteins. Our deletion analysis indicates that a specific region of Btf prevents its speckle localization, and that removing this region directs Btf to nuclear speckles. Ongoing studies aim to determine if this regulation occurs via post-translational modification of Btf, or by intermolecular interactions with binding partners.

References:
1.Saitoh, N. et al., 2004. Mol. Biol. Cell 15: 3876-3890.
2.Merz, C. et al., 2007. RNA. 13:1-13.

Keywords: splicing, Btf