MRG15, a novel chromodomain protein, is present in two distinct multiprotein complexes involved in transcriptional activation.
MRG15 is a novel chromodomain protein that is a member of a family of genes related to MORF4. MORF4 (mortality factor on chromosome 4) induces senescence in a subset of human tumor cell lines. Our previous results indicated that MRG15 (MORF-related gene on chromosome 15) could derepress the B-myb promoter by association with Rb. In this study, sucrose gradient analysis demonstrated that MRG15 was present in two distinct nuclear protein complexes, MAF1 (MRG15-associated factor 1) and MAF2. Rb was associated with MRG15 and PAM14 (a novel coil-coil protein) in MAF1, and a histone acetyl transferase, hMOF, was an MRG15 partner in MAF2. Analysis of deletion mutants of MRG15 indicated that the leucine zipper at the C-terminal region of MRG15 was important for the protein associations in MAF1 and that the N-terminal chromodomain was required for the assembly of the MAF2 protein complex. Consistent with these data was the fact that a histone acetyltransferase activity associated with MRG15 was lost when the chromodomain was deleted and that both mutant MRG15 proteins failed to activate the B-myb promoter. The various mechanisms by which MRG15 could activate gene transcription are discussed.
Pardo
Patricia S
PS
Roy M. and Phyllis Gough Huffington Center on Aging, Baylor College of Medicine, Houston, Texas 77030, USA.
Leung
James K
JK
Lucchesi
John C
JC
Pereira-Smith
Olivia M
OM
D000123:Acetyltransferases / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D002467:Cell Nucleus / Q000378:metabolism / Q000473:pathology; D002868:Chromosomal Proteins, Non-Histone / Q000235:genetics* / Q000378:metabolism; D002884:Chromosomes, Human, Pair 15; D003001:Cloning, Molecular; D020570:Genes, myb; D051548:Histone Acetyltransferases; D006801:Humans; D008969:Molecular Sequence Data; D009698:Nucleoproteins / Q000235:genetics*; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic; D015183:Restriction Mapping; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism; D015534:Trans-Activators / Q000235:genetics* / Q000378:metabolism; D015533:Transcriptional Activation; D014407:Tumor Cells, Cultured
D002868:Chromosomal Proteins, Non-Histone; C471162:MRG15 protein, mouse; D009698:Nucleoproteins; D029701:Saccharomyces cerevisiae Proteins; D015534:Trans-Activators; D000123:Acetyltransferases; D051548:Histone Acetyltransferases