Analysis of Son Localization throughout mitosis and its involvement in mitotic defects

Abstract

<p>During the cell cycle, DNA is replicated and then precisely divided during cell division (mitosis) in order to generate two daughter cells. During metaphase of mitosis, chromosome segregation relies on the assembly of a mitotic spindle comprised of microtubules that attach to and segregate sister chromatids to daughter cells. Son is a large nuclear speckle protein that was found in the proteomic analysis of human mitotic spindles. Recent data from the Bubulya lab shows that Son is essential for nuclear speckle organization as well as for progression through metaphase of mitosis. This suggests that Son may have some functional role in organizing pre-mRNA processing factors, and it may also regulate cell cycle progression. Localization of Son during mitosis is not known. If Son is involved in mitotic spindle function, it may co-localize with microtubules during mitosis. High resolution microscopy was used to analyze localization of Son throughout mitosis and to compare the localization of Son with respect to spindle microtubules. A less well studied mitotic mechanism involves reestablishing nuclear organization, for example the assembly of nuclear speckles, following mitosis. We also compared localization of Son and the pre-mRNA processing factor Splicing Factor 2/ Alternative Splicing Factor (SF2/ASF). Son co-localizes with SF2/ASF in nuclear speckles during interphase. During mitosis, it may also localize to mitotic interchromatin granule clusters {MIGsL which are mitotic equivalent of nuclear speckles. In order to determine if Son localizes in MIGs we compared the localization of SF2 and Son during mitosis. If Son is important for seeding nuclear speckle assembly we hope to find it is localized in MIGs during mitosis and that it is required for MIG assembly. To pinpoint exact roles for Son during mitosis, future work will involve analysis of mitotic spindle organization and MIG assembly in Son-depleted cells.</p><p>This presentation occurred at the Wright State University Campus-Wide Celebration of Research, Scholarship and Creative Activities on April 16, 2010</p>