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Mu promoter activity

Philip W Becraft becraft at iastate.edu
Thu Sep 14 10:36:22 EST 2000

Proc Natl Acad Sci U S A 1991 Apr 15;88(8):3502-6

Inactivation of maize transposon Mu suppresses a mutant phenotype by activating
an outward-reading promoter near the end of Mu1.

Barkan A, Martienssen RA

Department of Plant Biology, University of California, Berkeley 94720.

We described previously a mutation in maize, hcf106, caused by the 
insertion of a Mu1 transposon. When the Mu transposon system is in an 
active phase, hcf106 conditions a nonphotosynthetic, pale green 
phenotype. However, when the Mu system is inactive (a state 
correlated with hypermethylation of Mu elements), the plant adopts a 
normal phenotype despite the continued presence of the transposon 
within the gene. The molecular mechanisms that mediate this 
suppression of the mutant phenotype have now been investigated. We 
show here that the Mu element responsible for the hcf106 lesion lies 
within sequences encoding the 5'-untranslated leader of the Hcf106 
mRNA. When the Mu transposon system is active, this insertion 
interferes with the accumulation of mRNA from the hcf106 allele. 
However, when Mu is inactive, mRNA similar in size and abundance to 
that transcribed from the normal allele accumulates. These 
transcripts initiate at many sites throughout a 70-base-pair region, 
within and immediately downstream of the Mu1 insertion. Thus, an 
unusual promoter spanning the downstream junction between Mu1 and 
Hcf106 substitutes for the normal Hcf106
promoter but only when Mu is inactive. The pattern of mRNA 
accumulation in different organs and in response to light suggests 
that the activity of this promoter is conditional not only upon the 
phase of Mu activity, but also upon signals that regulate the normal 
Hcf106 promoter.

MeSH Terms:
Base Sequence
DNA Transposable Elements*
Gene Expression Regulation*
Genes, Suppressor
Molecular Sequence Data
Promoter Regions (Genetics)*
RNA, Messenger/genetics
Support, U.S. Gov't, Non-P.H.S.
Support, U.S. Gov't, P.H.S.
Transcription, Genetic

Gene Symbols:

RNA, Messenger
DNA Transposable Elements

Grant support:

PMID: 1849660, UI: 91195379

At 01:08 PM 9/5/00 +0100, you wrote:
>Dear All,
>Does anybody know of an example where the insertion of Mutator into
>the 5'UTR of a maize gene has resulted in the Mu promoter(s) driving
>the expression of that gene?  If such a case exists what happens when
>Mu becomes methylated?
>Keith Edwards
>Head of Crop Genetics
>IACR-Long Ashton Research Station
>University of Bristol
>Long Ashton
>BS41 9AF
>Tel: 01275 549431
>Fax: 01275 394281
>Email: keith.edwards at bbsrc.ac.uk

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