In searching the human genome for gene sequences that specify general transcription factors (GTFs), and transcriptional activators, the researchers found sequences for numerous genes that were similar to those in yeast and the fruitfly Drosophila. However, they also found many more human gene sequences than in the Drosophila genome that appear to be related to a particular GTF, called TFIID, "indicating that the potential diversity of human TFIID is much greater than that of Drosophila."
In searching for transcriptional activators, the researchers found more than 2,000 genes that could code for these proteinsfar more than they found in genome databases for Drosophila and the roundworm C. elegans. "This search illustrates how the human genome sequence will provide many new factors that may be involved in gene expression, although their roles remain unknown," wrote the scientists.
Similarly in a search for genes that encode proteins involved in assembling the mRNA splicing machinery, the scientists found "significantly greater complexity than is found in Drosophila." And, in searching for genes that encode proteins involved in adding the poly(A) tail to mRNA, the researchers unexpectedly found new genes, which, again, suggests that humans have a more complex gene expression machinery.
Green said, "in each case, the surprises are of the same type. When we looked for genes for certain types of proteins that were homologs to Drosophila, there was no reason to believe there would be more than a single protein. But in fact, we found homologs that there was no reason to suspect would be there."
The researchers pointed out, however, that "although these searches highlight the power of the
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Contact: Jim Keeley
keeleyj@hhmi.org
301-215-8858
Howard Hughes Medical Institute
11-Feb-2001