%0 Journal Article
%T Control of dinucleoside polyphosphates by the FHIT-homologous HNT2 gene, adenine biosynthesis and heat shock in Saccharomyces cerevisiae
%A Marta Rubio-Texeira
%A James M Varnum
%A Pawel Bieganowski
%A Charles Brenner
%J BMC Molecular Biology
%D 2002
%I BioMed Central
%R 10.1186/1471-2199-3-7
%X Here we demonstrate that dinucleoside polyphosphate levels increase 500-fold to hundreds of micromolar in strains devoid of the Saccharomyces cerevisiae homolog of Fhit, Hnt2. Accumulation of dinucleoside polyphosphates is reversed by re-expression of Hnt2 and is active site-dependent. Dinucleoside polyphosphate levels depend on an intact adenine biosynthetic pathway and time in liquid culture, and are induced by heat shock to greater than 0.1 millimolar even in Hnt2+ cells.The data indicate that Hnt2 hydrolyzes both ApppN and AppppN in vivo and that, in heat-shocked, adenine prototrophic yeast strains, dinucleoside polyphosphates accumulate to levels in which they may saturate Hnt2.The human FHIT gene, located at the chromosome 3 fragile site FRA3B, is inactivated early in the development of many tumors [1]. Murine Fhit is also located at a fragile site [2,3] and mice heterozygous for disruption of Fhit, given low intragastric doses of the mutagen N-nitrosomethylbenzylamine, develop stomach and sebaceous tumors [4] that can be prevented by viral Fhit expression [5]. Fhit, a dimer of 147 amino acid subunits, is a member of the histidine triad (HIT) superfamily of nucleotide hydrolases and transferases [6,7]. Members of the Hint branch of the HIT superfamily are found in all forms of life [8]. The S. cerevisiae Hint homolog, Hnt1, and rabbit Hint possess adenosine monophosphoramidase activity that functions in yeast to positively regulate function of Kin28, Ccl1 and Tfb3, which constitute the kinase component of general transcription factor TFIIH [9]. A new Hint related protein, Aprataxin, is mutated in individuals with ataxia with oculomotor apraxia [10,11] and has a yeast homolog termed Hnt3 [9]. Members of the Fhit branch of the HIT superfamily have been found in fungi [12,13], animals [2,14,15] and plants [7] and hydrolyze diadenosine tetraphosphate, diadenosine triphosphate and other 5'-5"'-dinucleoside polyphosphates. The middle histidine of the histidine triad
%U http://www.biomedcentral.com/1471-2199/3/7