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April 14, 2005

Gene Splicing

New study explains process leading to many proteins from one gene.

"Alternative splicing appears to occur in 30 percent to 60 percent of human genes, so understanding the regulatory mechanisms guiding the process is fundamentally important to almost all biological issues,"

“Using computers, the UT Southwestern researchers scanned the human genome and found that the presence of certain DNA sequences called "tandem repeats" that lie between exons are highly correlated with the process of alternative splicing. They found a large number of tandem repeats on either side of exons destined to be spliced out of the pre-mRNA. The tandem repeat sequences also were complementary and could bind to each other.

"The complementary tandem repeat sequences on either side of an exon allow the DNA to loop back on itself, bind together, pinch off
the loop containing a particular exon and then splice it out," Dr. Garner explained. “

“Tandem repeats are "hot spots" where errors can easily be made during the copying process; for example, an extra CA could be added or deleted from the correct sequence. These errors could then result in a gene improperly splicing out an exon, thus making the wrong protein, Dr. Garner said.”

Fly comment: This may be an example of how the animal genome supports fast evolution. The DNA hot spots mutate causing protein pieces to combine in new ways to form new proteins. The protein pieces could be viewed as subroutines that can be combined to form new functions.

Posted by fly at 01:10 PM