A SURVEY OF GENE EXPRESSION AND DIVERSITY IN THE VENOM GLANDS OF THE PIT VIPER  Bothrops insularis THROUGH THE GENERATION OF EXPRESSED SEQUENCE TAGS (ESTS)

Azevedo, I.L.M.J.(1), Ho, P.L.(1)

(1)Centro de Biotecnologia, Instituto Butantan, São Paulo, SP, Brasil

In order to produce a global panorama of the transcriptional activity of snake venom glands and to correlate this with its venom composition, we constructed a plasmidial cDNA library from B. insularis mRNA, which was validated by restriction analysis of sample clones and used to generate an Expressed Sequence Tags (ESTs) database. Good quality sequences were obtained from 610 independent clones, clustered in unique genes and further analyzed by similarity comparison with molecular databases. These analyses revealed the putative identification of 210 distinct gene products. Toxin sequences correspond to 56% of all transcripts (85 clusters), metalloproteinases (23%) and the bradykinin-potentiating peptides (BPPs) (11%) being the major components. This approach revealed a new highly expressed toxin similar to vascular endothelial growth factor (VEGF), which was recently reported (Junqueira-de-Azevedo et al., (2001) J. Biol. Chem. 276 pp. 39836). Among the 125 clusters matching cellular proteins, the major part represents molecules involved in gene and protein expression, notably in disulfide bond assembly, reflecting a high specialization of this tissue for toxin synthesis. An unusual representation of retrotransposon-like sequences was also found and could be related to the occurrence and diversity of many paralogous forms of toxins in venom gland. In conclusion, our B. insularis dbEST allowed the identification of the most common classes of toxins present in Viperidae venoms, which parallels the complex hemorrhagic effects evoked by the venom on the prey. In addition, it provides the first comprehensive set of reptilian gene sequences described so far.

Support: FAPESP, CNPq and Fundação Butantan.

CORRESPONDENCE TO:

Inácio de Loiola Meirelles Junqueira de Azevedo, Rua Dr. Queiróz Guimarães, 640, São Paulo, SP, CEP: 05609-000, Brasil, Email: ijuncaze@usp.br