ID OF A SITE IN MEF2D THAT IS MODIFIED BY O-LINKED N-ACETYLGLUCOSAMINE

University Of California, San Francisco, San Francisco CA

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Abstract

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Mef2D (Myocyte enhancer binding factor 2D) belongs to a family of four transcription factor namely Mef2A, Mef2B, Mef2C and Mef2D. This family of transcription factor shares a highly conserved MADS (MCM1, Agamous, Deficiens, SRF) domain, as well as a unique MEF2 domain. These two domains together constitute the N-terminal 87 amino acids of the MEF2 transcription factors, and mediate DNA binding, dimerization, and interaction with multiple coactivators and corepressors. The C-terminal domain of this family is more divergent and contains the transcriptional activation domain (TAD). The activity of Mef2D is regulated by multiple post-translational modifications. Mef2D is known to be phosphorylated, acetylated and sumoylated. A relatively newly identified modification, O-linked N-acetyl glucosamine (O-GlcNAc), is an abundant post-translational modification that modulates function of several phospho-proteins with diverse cellular functions. O-GlcNAc modifies serines and threonines of nuclear and cytoplasmic proteins and the modified proteins have important function in protein-protein interaction, transcription and signal transduction. O-GlcNAc exists in a complex interplay with phosphorylation and in many cases phosphorylation has been found to be reciprocal to O-GlcNAc. Our studies, using antibody against O-GlcNAc, show that Mef2D is modified by O-GlcNAc. To understand the function of Mef2D glycosylation, we need to identify the site of modification. Identification of the site will allow us to mutate the site and perform further analysis. The UCSF Mass Spectrometry Facility will help us with this part of the project to identify the site of O-GlcNAc and also help us identify if the same site is also modified by phosphorylation.