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MLL3 and MLL4 Methyltransferases Bind to the MAFA and MAFB Transcription Factors to Regulate Islet β-Cell Function

Insulin produced by islet β-cells plays a critical role in glucose homeostasis, with type 1 and type 2 diabetes both resulting from inactivation and/or loss of this cell population. Islet-enriched transcription factors regulate β-cell formation and function, yet little is known about the molecules r...

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Detalles Bibliográficos
Autores principales: Scoville, David W., Cyphert, Holly A., Liao, Lan, Xu, Jianming, Reynolds, Al, Guo, Shuangli, Stein, Roland
Formato: Online Artículo Texto
Lenguaje:English
Publicado: American Diabetes Association 2015
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4613979/
https://www.ncbi.nlm.nih.gov/pubmed/26180087
http://dx.doi.org/10.2337/db15-0281
Descripción
Sumario:Insulin produced by islet β-cells plays a critical role in glucose homeostasis, with type 1 and type 2 diabetes both resulting from inactivation and/or loss of this cell population. Islet-enriched transcription factors regulate β-cell formation and function, yet little is known about the molecules recruited to mediate control. An unbiased in-cell biochemical and mass spectrometry strategy was used to isolate MafA transcription factor–binding proteins. Among the many coregulators identified were all of the subunits of the mixed-lineage leukemia 3 (Mll3) and 4 (Mll4) complexes, with histone 3 lysine 4 methyltransferases strongly associated with gene activation. MafA was bound to the ∼1.5 MDa Mll3 and Mll4 complexes in size-fractionated β-cell extracts. Likewise, closely related human MAFB, which is important to β-cell formation and coproduced with MAFA in adult human islet β-cells, bound MLL3 and MLL4 complexes. Knockdown of NCOA6, a core subunit of these methyltransferases, reduced expression of a subset of MAFA and MAFB target genes in mouse and human β-cell lines. In contrast, a broader effect on MafA/MafB gene activation was observed in mice lacking NCoA6 in islet β-cells. We propose that MLL3 and MLL4 are broadly required for controlling MAFA and MAFB transactivation during development and postnatally.