GENOMIC ORGANIZATION AND EXPRESSION OF 2 INDEPENDENT GENE ARRAYS CODING FOR 2 ANTIGENIC ACIDIC RIBOSOMAL-PROTEINS OF LEISHMANIA

In the present paper we describe the isolation and characterization of four novel genes of the parasitic protozoan Leishmania infantum. Thes e genes are organized as two independent gene clusters, and they are r elated by nucleotide sequence to eukaryotic genes encoding acidic ribo somal proteins. Each gene cluster contains two tandemly linked genes c oding for identical proteins. Each of the proteins coded by the gene c lusters (called LiP and LiP') are highly divergent in sequence, showin g the characteristic features of eukaryotic P-proteins from the P2 gro up. In spite of the sequence conservation of the coding regions of eac h of the genes in the cluster, the 5'- and 3'-untranslated regions are heterogeneous in sequence. The analysis of the expression of these ge nes indicates that logarithmic phase promastigotes show increased leve ls of LiP- and LiP'-specific transcripts compared with stationary phas e promastigotes. The steady state RNA levels of the LiP and LiP' genes show a similar dependence of the growth phase of the parasite. Using specific probes for the divergent 3'-untranslated regions of each of t he genes, it was found that the abundance of the mature transcripts is different even when the transcripts are derived from the same gene cl uster. These findings probably indicate that the 3'-untranslated regio ns may influence the stability or turnover of the transcripts derived from both LiP and LiP' gene clusters.