Differentiation and proliferation are known to be influenced by steroid stimulation. The activity of the steroid receptor activator (SRA) RNA, an epigenetic regulatory component in the steroid receptor coactivator-1 (SRC-1) acetyltransferase complex, is needed for a response to steroid hormones by tumor cells. However, this activity is hindered by suppressive RNA binding proteins like the SMART/HDAC1-associated repressor protein (SHARP), which binds the STR7 domain of SRA RNA through its four RNA recognition motifs (RRMs); but it is not fully understood how SHARP executes this role as there are no SRA RNA-SHARP structures available for study. Traditional methods have determined the structures of SHARP RRMs, but these techniques are limited when it comes to SRA RNA-SHARP complexes because of its size and flexibility. In this study, SHARP2 was purified and complexed with STR7 RNA synthesized from T7 polymerase transcription using oligonucleotides. Small angle x-ray scattering was then used to investigate and compare the structures of the three-dimensional conformations of SRA RNA-SHARP2 complexes to the free-SHARP2 and the free-STR7 RNA structures, to better understand how SHARP carries its function and thereby improve therapeutic treatments for cancer. The data obtained showed structural changes in the RNA and an increase in the radius of gyration, supporting the hypothesis that SHARP RRM2 contributes to a reduction in the SRA RNA coactivator activity by remodeling the RNA structure while the remaining SHARP RRMs may act simply as recruitment modules.

Small Angle X-Ray Scattering study of conformational changes in steroid responsive activator (SRA) RNA upon binding repressor protein (SHARP)

2019 Spring National Meeting

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