Presentation: Up-regulation of 150kDa Adenosine Deaminase that Act on RNA(ADAR1) Gene Expression and Altered Editing of ADAR2 Gene Transcripts in Physiologically Activated T Lymphocytes (2007)

152 Up-regulation of 150kDa Adenosine Deaminase that Act on RNA(ADAR1) Gene Expression and Altered Editing of ADAR2 Gene Transcripts in Physiologically Activated T Lymphocytes

RNA editing plays an important role in the regulation of gene expression and produces phenotypic variability. We and other investigators demonstrated up-regulation of RNA editing gene, 150-kDa ADAR expression in SLE PBMCs, NK cells, T cells and B cells. The presence of a small proportion of activated T cells is the hallmark of SLE. Therefore, it was hypothesized that 150-kDa ADAR1 gene expression is partially induced by the physiological activation of T cells. To examine this hypothesis, T cells are activated by antiCD3-ε + antiCD28 for various time periods from 0 to 48hrs. The expression of 110-kDa, 150-kDa ADAR1, and IL2 and GAPDH gene transcripts was analyzed. The 110-kDa and 150-kDa ADAR1 gene expression was quantified at transcript and protein level by using competitive PCR and western blotting. Four to six fold increase in the 150-kDa ADAR1 gene transcript was observed at the 18hr time point. A decrease was noticed at 24hr and background level was reached by 48hr. The150-kDa ADAR1 protein expression was up-regulated at 24hr period and peaked by 48hr. No significant change was observed in the 110-kDa ADAR gene expression at any of the time points. ADAR2 gene transcripts are substrates for ADAR1 and 2 enzymes. Therefore, we assessed the role of 150-kDa ADAR enzyme in editing of IFNAR2 gene transcripts of normal and activated T cells. For these analysis 48hr. time point has been selected, since the150-kDa ADAR1 protein expression was peaked at this time point. Sequence analysis demonstrated A to I editing at -1, +10, + 23 and +24 in normal T cells. In activated T cells site selective editing of the -2 site was observed. Previous studies indicate that this site is predominantly edited by ADAR1. In addition to these, novel editing sites at -56, -19 base positions were also identified in activated T cells. The occurrence of novel editing at specific sites exclusively in ADAR2 gene transcripts of activated T cells may be due to up-regulation of ADAR1 and/or formation of ADAR1 and ADAR2 heterodimers which might have more affinity for the observed novel edited sites. Based on these results, it is proposed that, 150-kDa ADAR1 gene expression was selectively induced in T cells by antiCD3-ε + anti CD28 stimulation and its possible role in site selective editing in gene transcripts and altering the functions of several gene products of T cells during proliferation and development.

  D. Laxminarayana, This work was supported by National Institutes of Health Grant AR48628 (to D.L)., 2; I.U. Khan, None; B. Giri, None; C.E. Samuel, None.