Characterization of the Histone Acetyltransferase (HAT) Domain of a Bifunctional Protein with Activable O-GlcNAcase and HAT Activities

Abstract

Histones and transcription factors are regulated by a number of post-translational modifications that in turn regulate the transcriptional activity of genes. These modifications occur in large, multisubunit complexes. We have reported previously that mSin3A can recruit O-GlcNAc transferase (OGT) along with histone deacetylase into such a corepressor complex. This physical association allows OGT to act cooperatively with histone deacetylation in gene repression by catalyzing the OGlcNAc modification on specific transcription factors to inhibit their activity. For rapid, reversible gene regulation, the enzymes responsible for the converse reactions must be present. Here, we report that O-GlcNAcase, which is responsible for the removal of O-GlcNAc additions on nuclear and cytosolic proteins, possesses intrinsic histone acetyltransferase (HAT) activity in vitro. Free as well as reconstituted nucleosomal histones are substrates of this bifunctional enzyme. This protein, now termed NCOAT (nuclear cytoplasmic O-GlcNAcase and acetyltransferase) has a typical HAT domain that has both active and inactive states. This finding demonstrates that NCOAT may be regulated to reduce the state of glycosylation of transcriptional activators while increasing the acetylation of histones to allow for the concerted activation of eukaryotic gene transcription.

HATs and HDACs: from structure, function and regulation to novel strategies for therapy and prevention

“…Related to this, PCAF and p300 possess intrinsic E3 and E4 ubiquitin ligase activities, respectively (Grossman et al, 2003;Linares et al, 2007). Moreover, an O-linked N-acetylglucosamine (O-GlcNAc) transferase contains a HAT domain (Toleman et al, 2004), whereas a putative demethylase domain is present in Elp3 (Chinenov, 2002). Ubiquitin protease 8 associates with Gcn5 in SAGA (Baker and Grant, this issue).…”

Chemical approaches to understanding O-GlcNAc glycosylation in the brain

“…OGA contains an N-terminal glycosidase domain and a putative Cterminal histone acetyltransferase (HAT) domain 31 . Two distinct isoforms of OGA exist, a 130-kDa and a 75-kDa variant, which share the same catalytic domain but differ in their C terminus 32 .…”

A lipid-droplet-targeted O-GlcNAcase isoform is a key regulator of the proteasome

“…The full-length OGA long form (OGA-L) has 916 amino acids transcribed from 16 exons (NM_012215) and a short isoform (OGA-S) contains 677 amino acids transcribed from first 10 exons (AF307332). Both isoforms are identical at the N-terminal hyaluronidase domain, but differ in that OGA-L has a histone acetyl transferase (HAT)-like domain at the C-terminus (Schultz and Pils, 2002;Toleman et al, 2004;Whisenhunt et al, 2006). The OGA-S isoform continues transcription through exon 10, skipping the splice junction and terminating with a unique 14 amino acid tail.…”