A survey of Leishmania braziliensis genome by shotgun sequencing.

We have carried out a survey of the genome of Leishmania (Viannia) braziliensis by shotgun sequencing. Approximately 15% of the haploid genome of the parasite (5.15 Mb of genomic sequence) was obtained. A large number of known and putative genes, predicted to be involved in several cellular processes, were identified. Some genomic features were investigated, such as the general G + C content, which was found to be lower than L. major (57% versus 63%). BlastN searches revealed that 60.2% of the clusterized GSS sequences displayed similarity to L. major genomic sequences, while a BlastX search showed that 45.3% of the thus obtained predicted protein sequences showed similarity to annotated proteins of L. major. Further comparison of the degree of conservation between L. major and L. braziliensis revealed that coding regions are much more conserved than non-coding ones. The shotgun sequence analysis of Leishmania braziliensis appears to be an efficient and suitable strategy contributing to the search for vaccines and novel drug targets. The sequence data described in this paper have been submitted to the dbGSS database under the following accession numbers (BX530413 to BX530454; BX530456 to BX530718; BX538354 to BX539305; BX539350 to BX540325; BX541002 to BX544869; BX544893 to BX545685; BX897701 to BX897710; BX905184 to BX907797; BX907798 to BX908381; BX908403 to BX908718). All data including sequences are also available at (www.ebi.ac.uk/embl/).

Leishmania major chromosome 3 contains two long convergent polycistronic gene clusters separated by a tRNA gene.

Leishmania parasites (order Kinetoplastida, family Trypanosomatidae) cause a spectrum of human diseases ranging from asymptomatic to lethal. The approximately 33.6 Mb genome is distributed among 36 chromosome pairs that range in size from approximately 0.3 to 2.8 Mb. The complete nucleotide sequence of Leishmania major Friedlin chromosome 1 revealed 79 protein-coding genes organized into two divergent polycistronic gene clusters with the mRNAs transcribed towards the telomeres. We report here the complete nucleotide sequence of chromosome 3 (384 518 bp) and an analysis revealing 95 putative protein-coding ORFs. The ORFs are primarily organized into two large convergent polycistronic gene clusters (i.e. transcribed from the telomeres). In addition, a single gene at the left end is transcribed divergently towards the telomere, and a tRNA gene separates the two convergent gene clusters. Numerous genes have been identified, including those for metabolic enzymes, kinases, transporters, ribosomal proteins, spliceosome components, helicases, an RNA-binding protein and a DNA primase subunit.