Overexpressed Drosophila DNA methyltransferase 2 isoform C interacts with Hsp70 in vivo.
Shen and colleagues (Lin et al., 2004) have recently shown that overexpression of the Drosophila DNA methyltransferase 2 isoform C, dDnmt2c, extended life span of fruit flies, probably due to increased expression of small heat shock proteins such as Hsp22 or Hsp26. Here, I demonstrate with immunoprecipitations that overexpressed dDnmt2c interacts with endogenous Hsp70 protein in vivo in S2 cells. However, its C-terminal half, dDnmt2c(178-345) forms approximately 10-fold more Hsp70-containing protein complexe than wild-type dDnmt2c. Overexpressed dDnmt2c(178-345) but not the full length dDnmt2c is able to increase endogenous mRNA levels of the small heat shock proteins, Hsp26 and Hsp22. I provide evidence that dDnmt2c(178-345) increases Hsp26 promoter activity via two heat shock elements, HSE6 and HSE7. Simultaneously overexpressed Hsp40 or a dominant negative form of heat shock factor abrogates the dDnmt2c(178-345)-dependent increase in Hsp26 transcription. The data support a model in which the activation of heat shock factor normally found as an inactive monomer bound to chaperones is linked to the overexpressed C-terminus of dDnmt2c. Despite the differences observed in flies and S2 cells, these findings provide a possible explanation for the extended lifespan in dDnmt2c-overexpressing flies with increased levels of small heat shock proteins.
Institute of Molecular Biology, Academia Sinica, Nankang, Taipei 115, Taiwan, Republic of China. k.roder@hw.ac.uk
Karim
K
Roder
D000818:Animals; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000737:chemistry / Q000378:metabolism*; D029721:Drosophila Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000201:enzymology*; D015870:Gene Expression; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism*; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D007527:Isoenzymes / Q000378:metabolism; D011485:Protein Binding; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020218:Response Elements / Q000235:genetics; D015854:Up-Regulation / Q000235:genetics
D029721:Drosophila Proteins; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; C490752:Hsp22 protein, Drosophila; C087442:Hsp26 protein, Drosophila; D007527:Isoenzymes; D012333:RNA, Messenger; C491784:Mt2 protein, Drosophila; D004248:DNA (Cytosine-5-)-Methyltransferases