Restriction enzyme buffers and 5-azacytidine induce loss of protein and banding in plant metaphase chromosomes.

The incubation of root meristem of Vicia faba L. with 5-azacytidine for 72 h (5 cell cycles) resulted in shorter DNA fragments after digestion with a restriction enzyme Sau3A. Under the same condition in situ digestion of metaphase chromosomes with Sau3A revealed a stronger banding (C-banding-like) pattern in 5-azacytidine-treated chromosomes than in the control. This difference could hardly be attributed to the euchromatin demethylation as 5-azacytidine caused a loss of chromosomal proteins; similar effect was found as a result of incubation with some restriction endonuclease buffers which did not diminish the labeling with 3H-thymidine. After 5-azacytidine administration the entrance of cells into mitosis was delayed, the metaphase chromosomes were undercondensed and the pattern of DNA replication remained unchanged.