Stop codon read-through?

C. J. Fields cfields at gab.unt.edu
Wed Feb 19 02:55:45 EST 1997


Harris Laboratory wrote:
> 
> Is there any evidence for read-through on a UAG stop codon? If so what
> examples are available?
> 
> We have a cDNA sequence that contains an addition of 45 bp.  This
> causes an codon shift that results in a premature stop codon.  This
> should yield a 11 kDa protein when translated.  However in in vitro
> translation system, a 59 kDa protein is generated & detected via
> Western analysis.

Is this expressed in bacteria?  If so, it could very well be a
suppressor mutation for the UAG codon (from a mutant serine tRNA most
likely).  The tRNA mutation would be in the middle position, changing
the CGA anticodon to CUA (from 5' to 3'), or as shown below:

	tRNA        	3'---A-U-C---5'
	mRNA	    	5'---U-A-G---3'

Since a backup tRNA for serine is present (IGA, for the "wobble" of the
first three), the sacrifice is minimal as compared to other tRNA
possibilities (Leu, Trp, Tyr, Gln, Lys, Glu).

Then again, maybe I'm wrong...
 
-----------
C. J. Fields
Graduate Student, Dept. of Biological Sciences
The University of North Texas
Denton, TX 

email : cfields at gab.unt.edu
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