Cloning and characterization of a repetitive sequence fromPneumocystis carinii

Abstract

Four repetitive sequence clones measuring 10.9–23.4 kb in length were isolated from the genomic library ofPneumocystis carinii. Restriction enzymes mapping and cross-hybridization studies revealed that these clones are interrelated and that they derive from the common repeat unit, which is specific forP. carinii. Dot-blot analysis suggested that the copy number of the repeat sequence is about 100, assuming that the genome size is 1.5×10⁷ bp. Interestingly, the repetition unit extended over at least 23.4 kb and included long, 5.2-kb inverted repeats, for example, A-B-A′-C, in which A′ is the inversion of A.