Functional analysis of the B′ subunit of Arabidopsis protein phosphatase type 2A

Type 2A serine/threonine protein phosphatases (PP2A) have been identified as critical control elements of a number of eukaryotic cellular processes. The activity of the catalytic subunit of the enzyme is modulated by a variety of regulatory subunits. Here we present evidence regarding the chromosomal position of two distinct PP2A B' regulatory subunits genes: AtB'gamma and AtB'delta. We show these two genes are present on distinct chromosomes, as is the case for a number of other PP2A subunit genes. In addition, we present evidence that a translational enhancer exists within the 5' untranslated region (UTR) of transcripts derived from the AtB'gamma gene. Transgenic plants carrying 35S-5' UTR-beta-glucuronidase (GUS) constructs show a significant increase in GUS activity compared with plants carrying only the 35S-GUS insert. Northern blots indicate this enhancer does not cause increased mRNA stability but rather appears to serve to enhance translation initiation. In addition we show this translational enhancer appears to functions under different environmental conditions. Taken together these data suggest Arabidopsis cells may use translational control to determine levels of the AtB'gamma regulatory subunit and hence PP2A subunit composition/function. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.