[Show abstract][Hide abstract] ABSTRACT: We have examined the metaphase chromosomal localization of 15 proteins that have previously been described as involved in mammalian chromatin modification and/or transcriptional modulation. Immunofluorescence data indicate that all the proteins localize to human and mouse centromeres, a neocentromere, and the active centromere of a dicentric chromosome, with six of these proteins (Sin3A, PCAF, MYST, MBD2, ORC2, P300/CBP) being demonstrated at mammalian centromeres for the first time. Most of these proteins fall into two distinct chromosomal distribution patterns: (a) kinetochore-associated proteins (Sin3A, PCAF, MYST and BAF180), which colocalize with metaphase kinetochores, but not any of the pericentric and other major heterochromatic regions; and (b) heterochromatin-associated proteins (MeCP2, MBD1, MBD2, ATRX, HP1alpha, HDAC1, HDAC2, DNMT1 and DNMT3b), which colocalize with centromeric/pericentric heterochromatin and all other major heterochromatic sites. A heterogeneous third group (c) consists of the origin recognition complex subunit ORC2 and the histone acetyltransferase P300/CBP, which associate generally with kinetochores in humans and centromeric/pericentric heterochromatin in mouse, with some minor differences in localization. These observations indicate an extensive sharing of protein components involved in chromatin modification at gene loci, centromeres and various chromosomal heterochromatic landmarks. The definition of distinct patterns of chromosomal distribution for these proteins provides a useful basis for the further investigation of the broad-ranging roles of these proteins.
Full-text · Article · Jan 2004 · Human Molecular Genetics
[Show abstract][Hide abstract] ABSTRACT: Recent data in yeast and Drosophila suggest a domain-like centromere structure with a modified chromatin core and flanking regions of heterochromatin. We have analyzed a functional human centromere and defined a region of increased chromosome scaffold/matrix attachment that overlaps three other distinct and nonoverlapping domains for constitutive centromere proteins CENP-A and CENP-H, and heterochromatin protein HP1. Transcriptional competency is intact throughout the S/MAR-enriched region and within the CENP-A- and CENP-H-associated chromatin. These results provide insights into the relationship between centromeric chromatin and transcriptional competency in vivo, highlighting the permissibility of transcription within the constitutively modified, nonheterochromatic chromatin of a functional eukaryotic centromere.