Relationship of HP1 proteins to centromeric heterochromatin characterized by the presence of H3(K9) and absence of H3(K4) dimethylation
|Year of publication
|Article in Proceedings
|Biophysics of the Genome
|MU Faculty or unit
|Genetics and molecular biology
|Recent studies have highlighted the importance of heterochromatin proteins HP1 (alpha,beta,gamma) in the nuclear structure organization. Patterns and levels of HP1 proteins and their relationship to specific histone methylations are associated with both heterochromatic and euchromatic loci. In this study we have examined arrangement of HP1 proteins and histone modifications related to the centromeric heterochromatin of human and mouse chromosomes. Focal arrangement of HP1beta was characterized by a smaller foci located closer to the nuclear periphery and larger foci associated with the nucleoli of human colon adenocarcinoma HT29 cells. Heterochromatin of selected centromeres (9cen,14/22cen,Ycen) co-localized with foci of HP1beta. Immuno-FISH analyses revealed that centromeres analyzed were H3(K9) dimethylated and absent of H3(K4) dimethylation studied in HT29 cells and in human small lung carcinoma cells A549. Chromatin immunoprecipitation analyses (ChIPs) determined the same histone methylation states for centromere of chromosome Y. Morphological differences were observed for beta-satellite centromeric regions of chromosome 9 that were more diffuse in comparison with more compact alpha-satellite sequences of chromosome 10. Distinct intephase patterns were found not only for H3(K9) and H3(K4) dimethylated regions of human cells but also for HP1 alpha, beta and gamma proteins in mouse embryonic carcinoma cells P19. Both HP1alpha and beta were associated with centromeric heterochromatin while many foci (but not all) of HP1gamma were found away from centromeres determined by DAPI staining.