Selective interactions of hnRNP M isoforms with the TET proteins TAF15 and TLS/FUS
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The molecular composition of macromolecular assemblies engaged in transcription and splicing influences biogenesis of mRNA transcripts. Preference for one over the other interactive protein partner within those complexes is expected to change the gene expression pattern and to affect subsequent cellular events. We report here the novel and selective associations between RNA-binding proteins, namely the hnRNP M1-4 isoforms—involved in early spliceosome assembly and alternative splicing—and the transcription factors TAF15 and TLS/FUS. In immunoprecipitation studies on HeLa nuclear extracts, TAF15 co-immunoprecipitates preferably with the higher molecular weight hnRNP M3/4 isoforms, opposite to TLS/FUS that associates with the lower molecular weight hnRNP M1/2 species. We demonstrate that these associations can be mediated through direct protein–protein interactions via the amino-termini of the TET proteins, independently of RNA. Finally, we show partial co-localization of TAF15 and TLS/FUS with hnRNP M proteins in HeLa nuclei, supporting the biochemically obtained data. The participation of hnRNP M in an expanding network of protein–protein interactions suggests its important functioning in the coordination of transcriptional and post-transcriptional events.
KeywordsTET proteins RNA-binding proteins hnRNP M mRNA processing
We thank Drs. L. Tora for the generous gift of the anti-TAF15, -TLS/FUS antibodies and W. van Venrooij of the anti-U2B” antibody. M.M. and M.L. were Marie Curie post-doctoral fellows working in the framework of the FP6 EU grant MTKD-CT-2004-509836 that also provided financial support for this work. The experimental work presented in the present report was performed in the auspices of the Institute of Biological Research and Biotechnology, currently a Division of the Institute of Biology, Medicinal Chemistry and Biotechnology.
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