GENERATION OF EXPRESSED SEQUENCE TAGS AS PHYSICAL LANDMARKS IN THE GENOME OF TRYPANOSOMA-BRUCEI

Previous molecular genetic studies on the African trypanosome have foc used on only a few genes and gene products, the majority of which are concerned with surface antigenic variation; consequently, an insignifi cant number of the genes of this organism have been characterized to d ate. In order to: (I) identify new genes and analyze their expression profile, (2) generate expressed sequence tags (ESTs) for derivation of a physical map of the trypanosome genome, and (3) make available the partial sequence information and the corresponding clones for general biomedical research on the parasite, we have performed single-pass seq uencing of random, directionally cloned cDNAs from a bloodstream form Trypanosoma brucei rhodesiense library. Analysis of 2128 such ESTs seq uenced so far in this study showed significant similarities [BLASTX P( n)-value < 10(-4), and a match > 10 amino acid residues] with proteins whose genes have been described in diverse organisms including man, r odents, kinetoplastids, yeasts and plants. A number of the ESTs encode homologues of proteins involved in various functions including signal reception and transduction, cell division, gene regulation, DNA repai r and replication, general metabolism, and structural integrity. Altho ugh some of these genes may have been expected to be present in the Af rican trypanosomes, the majority of them had not previously been descr ibed in these organisms. A large proportion, 768 individual ESTs (36%, representing 385 different transcripts), had a significant homology w ith genes described in organisms other than the African trypanosomes; however, 15% of the ESTs were from genes already described in trypanos omes. Among the ESTs analysed were 462 distinct known genes, only 77 o f which have been described in T. brucei. Approximately 52% of the EST s did not show any significant homology with the sequences in any of t he public domain databases. (C) 1998 Elsevier Science B.V. All rights reserved.