INTRONs CONSERVED!!!

norm eberhardt eberhard at Mayo.EDU
Fri Jun 17 07:53:12 EST 1994


In article <2to56r$a2t at mega.chem.ut.ee>, mspeek at ebc.ee (Mart Speek) writes:
|> HI again netwalkers;
|> 
|> This is my 2nd time to ask if anyone knows specific examples
|> of intron conservation between similar or different genes
|> (genes & references). I appreciate all responses I've got
|> so far. Please send messages to:
|> 
|> mspeek at itsa.ucsf.edu
|> 
|> Cheers
|> 
|> 
|> 

	A trivial example would be the very high degree of conservation between
the introns in the human growth hormone and chorionic somatomammotropin genes. 
These genes were duplicated relatively recently (15-60 Myr).  The exonic domains
retain about 93.5% sequence identity.  Curiously, the intronic domains exhibit
a somehwat higher degree of conservation, since they are about 96% identical. 
With the exception of pituitary GH, the genes' (5 in all; 1 pituitary GH, 
1 placental GH, 1 pseudogene and 2 placental CS genes) functions are not known
precisely; however, they do share some common activities, e.g., lactogenic
activity.  All of the genes are located on chromosome 17q and occupy a mere 50 kb
of DNA.  The locus has been sequenced (Genbank Accession #J03071).  For further 
information see:

Miller and Eberhardt, Endocrine Rev 4:97-130, 1983 and
Hirt et al, DNA 6:59-70, 1987

	I say trivial since it is not entirely clear what you are after and
because these genes have duplicated so recently.  I think it is interesting
that the sequence conservation within the introns is higher than the exonic 
domains.  At least the divergence in the exonic domains has resulted in genes
with demonstrably different activities and the divergence has also resulted in
the differential expression of these genes in the pituitary and placenta
respectively.  It is not clear that the intronic conservation serves any purpose.
Also, the GH and CS genes belong to the prolactin gene family and the introns of 
the PRL gene are entirely unlike those of their offspring.

norman eberhardt
eberhardt at mayo.edu



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