SEQUENCE DIVERSITY AND ORGANIZATION OF THE MSP GENE FAMILY ENCODING GP63 OF LEISHMANIA-CHAGASI

During in vitro growth Leishmania chagasi promastigotes differentially express 3 classes of RNAs encoding the major surface protease (MSP) g p63 that can be distinguished by their unique 3' untranslated regions [7]. Here we show that the three classes (logarithmic-specific, statio nary-specific and constitutively expressed) are encoded by a family of at least 4 tandem stationary genes (mspS2, mspSl, mspS3 and mspS5) fo llowed by twelve or more logarithmic genes (mspL genes), one constitut ive gene (mspC) and a final stationary gene (mspS4). Some of the stati onary genes can be distinguished from each other by groups of nucleoti de differences within the coding regions that result in localized amin o acid differences. Northern blots confirm that RNAs from the individu al stationary genes are present in stationary, but not logarithmic, ph ase promastigotes. Western blots using sera directed against synthetic peptides indicate that correspondingly heterogeneous gp63 proteins ar e expressed in L. chagasi promastigotes. A 200-bp region upstream of a ir three gp63 gene classes is conserved except for a variable number o f 6-bp repeats. Downstream of the gp63 coding regions are highly conse rved, class-specific sequences that include the 3' untranslated region s and extend past the polyadenylation site for 65 bp (mspL), 345 bp (m spC) or 2.8 kb (mspS). These sequence features flanking the msp coding regions are likely important in the growth phase-specific expression of the three gp63 RNA classes.