Leishmania major: Histone H1 gene expression from the sw3 locus

Histone H1 in the parasitic protozoan Leishmania is a developmentally regul ated protein encoded by the sw3 gene. Here we report that histone H1 varian ts exist in different Leishmania species and strains of L. major and that t hey are encoded by polymorphic genes. Amplification of the sw3 gene from th e genome of three strains of L. major gave rise to different products in ea ch strain, suggesting the presence of a multicopy gene family. In L.. major ; these genes were all restricted to a 50-kb Bg/II fragment found on a chro mosomal band of 1.3 Mb (chromosome 27). The detection of RFLPs in this locu s demonstrated its heterogeneity within several species and strains of Leis hmania. Two different copies of sw3 (sw3.0 and sw3.1) were identified after screening a cosmid library containing L. major strain Friedlin genomic DNA . They were identical in their 5' UTRs and open reading frames, but differe d in their 3' UTRs. With respect to the originally cloned copy of sw3 from L, major strain LV39, their open reading frames lacked a repeat unit of 9 a mino acids. Immunoblots of L. guyanensis parasites transfected with these c osmids revealed that both copies could give rise to the histone H1 protein. The characterization of this locus will now make possible a detailed analy sis of the function of histone H1 in Leishmania, as well as permit the diss ection of the molecular mechanisms governing the developmental regulation o f the sw3 gene, (C) 1999 Academic Press.