A NOVEL REPETITIVE SEQUENCE LIES NEAR THE GENE ENCODING A CYTOSINE METHYLTRANSFERASE IN THE CYANOBACTERIUM DACTYLOCOCCOPSIS-SALINA

An unusual cluster of tandemly repeated DNA sequences (TRS) was found downstream from the gene encoding DsaV methyltransferase, the DNA modi fication enzyme in the DsaV restriction-modification system found in a strain of Dactylococcopsis salina (Ds). The repeat unit is about 32-b p long and is present 13 times in the cluster. Each repeat unit can be divided into two distinct parts based on the level of sequence conser vation and evolution. Hybridization of Ds DNA with a probe specific fo r this cluster revealed that there were at least two additional sites within the genome with similar TRS. The TRS units are localized in one region of the Ds genome. They do not share significant sequence simil arity with other TRS found in prokaryotes.