There is much happening in genetics it's hard to know where to start listing the highlights. Here are some of the more interesting items I've come across recently:
Did DNA replication evolve twice independently?
by Leipe DD, Aravind L, Koonin EV. in
Nucleic Acids Res. 1999 Sep 1;27(17):3389-401.
DNA replication is central to all extant cellular organisms. principal proteins involved in transcription and translation, which are highly conserved in all divisions of life. We performed detailed sequence comparisons of the proteins that fulfill indispensable functions in DNA replication and classified them.
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Posted by ellen at September 13, 2007 07:58 AM
The universal conservation of some components of the DNA replication machinery and enzymes for DNA precursor biosynthesis but not the principal DNA polymerases [an enzyme that assists in DNA replication.] suggests that the last common ancestor (LCA) of all modern cellular life forms possessed DNA but did not replicate it the way extant cells do. We propose that the LCA had a genetic system that contained both RNA and DNA, with the latter being produced by reverse transcription. Consequently, the modern-type system for double-stranded DNA replication likely evolved independently in the bacterial and archaeal/eukaryotic lineages.
Artificial synthesis of a virus:
Cell-free, de novo synthesis of poliovirus
A Molla, AV Paul, and E Wimmer
http://www.sciencemag.org/cgi/content/abstract/254/5038/1647"Cell-free translation of poliovirus RNA in an extract of uninfected human (HeLa) cells yielded viral proteins through proteolysis of the polyprotein.
The origin of viruses and their possible roles in major evolutionary transitions
Virus Research Volume 117, Issue 1, April 2006, Pages 5-16
Comparative Genomics and Evolution of Complex Viruses
Patrick Forterre
Ancient virus resistance came at modern cost: Science Snapshot
The key difference seems to be a protein called TRIM5-alpha, variations of which are expressed by the genes of humans, apes and monkeys. "Each primate species encodes a TRIM5-alpha with a different antiviral specificity," write the study authors. "For example, TRIM5-alpha encoded by rhesus macaques renders them resistant to infection by HIV-1, but human TRIM5-alpha affords no such protection."
The human variant of TRIM5-alpha knocks the stuffing out of PtERV1, the researchers found, after dosing the resurrected retrovirus core with the protein.
Just one problem. TRIM5-alpha can either restrict PtERV1 or HIV, but not both, the team finds, after looking at the disease in apes and monkeys. The mutation needed to cancel out one disease robs it of the ability to combat the other.
So, the authors conclude, the human body is still primed to protect itself from a virus that has long been extinct, safeguards that have opened the door to the deadly impact of HIV.
