Satellite DNA spatial localization and transcriptional activity in mouse embryonic E-14 and IOUD2 stem cells

The formation of heterochromatin begins in the differentiating cells. The aim of this work was to study changes of satellite DNA distribution, transcriptional activity and interaction with certain proteins in mouse embryonic stem cells after induction with retinoic acid. We found that pericentromeric satellites entered chromocenters only some days after induction of E-14 and IOUD2 mouse embryonic stem cells. The redistribution was accompanied by association with HP1a and transcription from pericentromeric (but not centromeric) satellite DNA. RNA was polyadenylated and transcribed from the forward chain. Probes made from the cDNA hybridized to all chromosomes. In differentiating cells, the transcript was found exclusively in chromocenters while in differentiated cultured L929 cells it formed 1-2 large clusters outside chromocenters. Using ChIP and immunostaining, we demonstrated that in induced cells pericentromeric DNA interacted with RNA-helicase p68 that was previously shown to be involved in transcription regulation and to be involved in differentiation processes.