A single-stranded DNA-binding protein from Crithidia fasciculata recognizes the nucleotide sequence at the origin of replication of kinetoplast DNA minicircles.

A sequence-specific single-stranded DNA-binding protein from the trypanosomatid protozoan Crithidia fasciculata binds to a sequence of 12 nucleotides located at the origin of replication of kinetoplast DNA minicircles. This sequence, termed the universal minicircle sequence (UMS), is conserved in the kinetoplast DNA minicircles among species of the family Trypanosomatidae. The purified protein binds specifically to the heavy strand of the DNA at this site, which consists of the sequence 5'-GGGGTTGGTGTA-3'. Binding analyses using mutated UMS dodecamers have revealed the significant contribution of each of the individual residues at the binding site, with the exception of the 3'-terminal adenine residue, to the generation of specific protein-DNA complexes. The possible role of this sequence-specific single-stranded DNA-binding protein in replication of kinetoplast DNA minicircles and the relation of the UMS to chromosomal telomeric sequences are discussed.