The tissue and developmental specific expression of zein genes is highly regulated. It can be assumed that at least part of this regulation is achieved by trans-acting factors. This assumption is supported by genetic data with mutants such as opaque that affect zein protein production.
In this context we have started to look for the specific interactions of nuclear proteins with sequences lying upstream of cloned zein genes. In the case of pMS1, a clone containing a gene coding for a 19,000 dalton protein, we have shown by nitrocellulose filter binding and gel retention techniques several specific binding sites (see scheme). We have characterized one of these sites (at position -300) by footprint analysis and have shown a 22 bp protein binding site, which contained a 15 bp sequence that is found in all zein genes analyzed so far. Interestingly, this binding site can only be seen with nuclear extracts from endosperm tissue where the zein genes are specifically expressed. The other potential binding sites are being further characterized.
We conclude that the extensive flanking regions of zein genes are important for the regulation of the zein gene system, and more specifically for the interaction with the gene products of regulatory genes.
The first part of this work will be published in the January issue of the EMBO Journal.
U. Maier, J.W.S. Brown and G. Feix
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