A gene from the VSG expression site ofTrypanosoma bruceiencodes a protein with both leucine-rich repeats and a putative zinc finger

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Abstract
The transcription unit of the gene for the variant specific glycoprotein (VSG) AnTat 1.3A of Trypanosoma brucel contains several associated genes (ESAGs, for Expression Site-Associated Genes), 7 of which have already been described (1). We report here the characterization of a further ESAG, which we term ESAG 8, present 1 kb downstream from the putative adenylate cyclase gene ESAG 4. ESAG 8 encodes a 70 kd protein whose sequence indicates that it is probably not exposed at the cell surface. With the exception of the N-terminal domain which contains a presumptive DNA-binding zinc finger, the ESAG 8 protein consists exclusively of leucine-rich repeats of 23 amino acids, typical of protein-interacting domains such as the RAS-interacting region of the yeast adenylate cyclase. ESA-G 8 transcripts are only found in bloostream forms, and their level is particularly low, suggesting a high rate of degradation. The ESAG 8 protein may be involved in stage-specific regulatory processes, such as gene expression control or adenylate cyclase activation.