Trinucleotide repeats

Marnix L. Bosch marnix at u.washington.edu
Mon Dec 19 15:46:12 EST 1994


Hi, 

in response to the question outlined below, we have recently published a
hypothesis (J.Virol. 68:7566-7569, nov. 1994) on AAT triplet reiteration
in the HIV-1 envelope gene, followed by mutation and selection. Although
the mechanism is still unclear (to us at least), the end result is
accumulation of new N-linked glycosylation sites which would help the
virus escape from immune pressure. Hope this helps.

Marnix

In article <16 at reservoir.win-uk.net>, shane at reservoir.win-uk.net (Shane
McKee) wrote:

> Hi there!
> 
> I was wondering if anyone is aware of any published material on the
> role of trinucleotide repeats in the production of genetic
> variation, both within and between species. Variable Number Tandem
> Repeats (VNTRs) are regions of DNA which contain the same short
> sequence repeated many times, and can thus be described as (seq)n
> , where seq is a sequence of bases, eg CAG, ATGT, etc. These VNTRs
> of which trinucleotide repeats are a subset, often vary between
> individuals in the number of repeat units they contain, and can
> thus be used as informative polymorphisms for gene linkage
> analysis.
> 
>         In recent years, trinucleotide repeats have been linked to
> several inherited diseases, such as myotonic dystrophy,
> Huntington's disease and Fragile X syndrome. It seems that
> individuals affected by these diseases possess many more repeat
> units at the relevant locus than unaffected individuals, and the
> more repeats they have, the more severe the disease tends to be.
> 
>         In most textbook discussions of gene mutation ( forgive me
> for not keeping up with the literature ), attention seems to be
> focused on point mutations affecting the amino acid sequence of
> a protein, and thus its function. While undoubtedly important, it
> seems inadequate to explain some of the finely balanced properties
> of gene expression. VNTRs may be able to play a role in gene
> expression by being placed between a gene's promoter and the start
> of the exon, or between exons themselves, and the sheer physical
> DNA distance which must be transcribed may influence the success
> of the whole operation, and hence the expression of the protein.
> This could be potentially a very important mechanism for
> introducing genetic variation upon which evolution may act.
> 
>         Anyway, any thoughts on the matter?
>         
>         Thanks, 
>                 Shane
>                          
> 
> 
> Shane McKee [Shane at reservoir.win-uk.net]
>            " Art becomes Science when you start trying
>              to figure out what the hell you're doing. "
>                 NB: IMHO, MHO = *M*HO.



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