Association of modified cytosines and the methylated DNA-binding protein MeCP2 with distinctive structural domains of lampbrush chromatin

摘要: We have investigated the association of DNA methylation and proteins interpreting state with distinctive closed open chromatin structural domains that are directly observable in lampbrush chromosomes (LBCs) amphibian oocytes. To establish distribution LBCs MeCP2, one key binding 5-methylcytosine-modified (5mC), we expressed HA-tagged MeCP2 constructs Xenopus laevis Full-length was predominantly targeted to closed, transcriptionally inactive chromomere a pattern proportional chromomeric density consistent global role determining state. A minor fraction HA-MeCP2 also found associate domain, namely short region at bases some extended lateral loops. Expression oocytes deleted point mutants derived from Rett syndrome patients demonstrated determined by its 5mC-binding domain. examined more 5mC immunostaining axolotl confirmed suggested targeting intense staining chromomeres loop bases. In addition, longer loops interstitial regions could be clearly stained for 5mC. These corresponded precisely unusual segments active transcription units which RNA polymerase II (pol II) nascent transcripts were simultaneously absent. oxidized derivative, 5-hydroxymethylcytosine (5hmC). Although general, resembled obtained 5mC, antibody against 5hmC produced restricted chromosomal foci. foci third type but less structures formed clusters genes transcribed pol III. This raises possibility may play establishing patterns gene repression activation characterize specific III-transcribed families genomes.