NUDT2 Disruption Elevates Diadenosine Tetraphosphate (Ap(4)A) and Down-Regulates Immune Response and Cancer Promotion Genes

Marriott, Andrew S.; Vasieva, Olga; Fang, Yongxiang; Copeland, Nikki A.; McLennan, Alexander G.; Jones, Nigel J.

HINT1. This study was initiated by the suggestion of Razin and co-workers that direct activation of MITF and USF2 transcription complexes in mast-related cells occurred by Ap 4 Amediated displacement of the HINT1 co-repressor. For example, mast cell protease rMCP-6 (TPSB2), c-Kit (KIT), granzyme B (GZMB) and tryptophan hydroxylase (TPH1) were all upregulated in RBL cells either after direct introduction of Ap 4 A, after activation by IgE and antigen, or after increasing Ap 4 A by siRNA knockdown of NUDT2 [10, 31] . However, IPA 1 did not identify MITF (up 1.7-fold), USF2 or HINT1 (down 1.3-fold) as potential regulators in our study. Furthermore, TPSB2 was up 3.2-fold but KIT was down 2.3-fold and TPH1 unaffected (S2 and S3 Tables). No data were retrieved for GZMB. The USF2-responsive genes TGFB2, SHP (NR0B2), TERT and TSP-1 (THBS1) were also shown to be up-regulated by Ap 4 A in RBL cells [36] . In our study, USF2 expression was unchanged by NUDT2 knockout as was the very low-level expression of TGFB2, TERT and THBS (S2 Table) . No data were obtained for NR0B2. Elevated Ap 4 A was also found to activate the MITF-dependent transcription of myosin light chain 1a (MYL4) in cardiomyocytes [10] , but this gene is not expressed in KBM-7 cells. From a list of 113 genes shown to be up-regulated by MITF in melanoma [138] , 23 were up-and 20 down-regulated in NuKO cells, which would suggest that Ap 4 A-mediated MITF or USF2 activation is not prominent in our data.