Chromocenters are interphase nuclear landmark structures of constitutive heterochromatin. The tandem repeat (TR)-enriched parts of different chromosomes cluster together in chromocenters. There has been progress in recent years in determining the protein content of chromocenters, although it is not clear which DNA sequences underly constitutive heterochromatin apart from the TRs. The aim of the current work was to find out which DNA sequences besides TRs are involved in chromocenters' formation. Biochemically isolated chromocenters and microdissected centromeric regions were amplified by DOP-PCR, then cloned and sequenced. Alignment to Repbase, the mouse reference genome and WGS databases separated the sequences from both libraries into three groups: (1) sequences with similarity to pericentromere mouse major satellite; (2) sequences without similarity to any repetitive sequences; (3) sequences with similarity to long interspersed nuclear elements (LINEs). LINE-related sequences have a disperse pattern distri