Talk abstracts

Talk on Friday 01:10-01:30pm submitted by Alok Sharma

Probing Functions for Son in Nuclear Speckle Structure and Gene Expression.

Alok Sharma (Biomedical Sciences Ph.D. Program, Department of Biological Sciences, Wright State University), Sapna Varia (Biomedical Sciences Ph.D. Program, Department of Biological Sciences, Wright State University), Athanasios Bubulya (Department of Biological Sciences, Wright State University), Paula A. Bubulya (Department of Biological Sciences, Wright State University)

Abstract:
In mammalian cells, pre-mRNA splicing factors and other pre-mRNA processing factors are stored in nuclear bodies called nuclear speckles. Proteomic analysis of nuclear speckles reflected enrichment of splicing factors in nuclear speckles and revealed 33 novel speckle proteins including Son (Saitoh, N., C. S. Spahr, S. Patterson, P. Bubulya, A. F. Neuwald and D. L. Spector. 2004. Proteomic analysis of interchromatin granule clusters. Mol. Biol. Cell. 15:3876-3890). Son is a large protein (2564 amino acid length) that contains six types of repetitive sequences that cover approximately one-third of its sequence and that are not found in any other protein. This study aims to determine nuclear functions for Son in pre-mRNA transcription and splicing as well as in structural organization of speckles.
We have recently generated rabbit polyclonal antibodies against both the amino- and the carboxy-termini of Son. Immunofluorescence localization of endogenous Son with these antibodies shows colocalization of Son with splicing factor 2/alternative splicing factor (SF2/ASF) in nuclear speckles. In addition, we fused Son with yellow fluorescent protein (YFP) and stably expressed YFP-Son in Hela cells where it also co-localizes with SF2/ASF in nuclear speckles. Interestingly, Hela cells that are treated with Son siRNA oligos show a complete reorganization of nuclear speckle components (including SR proteins and snRNP proteins) from their typical irregular shape into a donut-like shape. The altered organization of nuclear speckles observed after Son depletion implicates Son in a novel and essential role in the structural maintenance of nuclear speckles. Ongoing studies will elucidate the recruitment of Son to gene loci, and will determine the domains of Son required for nuclear speckle integrity and gene regulation.

Keywords: nuclear speckles, gene expression