Mouse anti-Human AKTIP monoclonal antibody, clone 7H9

Loss of heterozygosity (LOH) on chromosome 16q is one of the most frequent genetic alterations in hepatocellular carcinoma (HCC). Our previous data showed that the smallest common deleted region was between D16S415 and D16S419, encompassed approximately by a 0.75 cM region on 16q12.2, suggesting that the putative tumour suppressor genes (TSGs) at this locus might be involved in the development of HCC. Of the four genes (CHD9, RBL2, AKTIP and RPGRIP1L) located in this region, only RPGRIP1L was downregulated in HCCs. Downregulation of RPGRIP1L was found in 91% (10/11) HCC cell lines and in 35% (14/40) HCCs, respectively. To investigate the role of RPGRIP1L in HCCs, we used the overexpression of RPGRIP1L in four HCC cell lines (HepG2, Huh6, Huh7 and Hep3B). Overexpression of RPGRIP1L suppressed colony formation of tumour cells. Conversely, expression of RPGRIP1LM (dominant negative form) in HCC cells enhanced colony formation. Furthermore, knockdown RPGRIP1L by RNA interference in SK-HepI cells promoted colony formation. Taken together, these data strongly suggest that RPGRIP1L might be the putative TSG in HCC. Moreover, we showed that Mad2, Survivin and Securin were elevated in RPGRIP1LM-HepG2 transfectants and RPGRIP1L-shRNA-SK-HepI transfectants. After knockdown of MAD2 in RPGRIP1L-shRNA-SK-HepI transfectants partly reverse cellular colony formation capability. These data suggest that RPGRIP1L suppresses anchorage-independent growth partly through the mitotic checkpoint protein Mad2. (c) 2009 Elsevier Ltd. All rights reserved.

Human AKTIP and mouse Ft1 are orthologous ubiquitin E2 variant proteins involved in telomere maintenance and DNA replication. AKTIP also interacts with A- and B-type lamins. These features suggest that Ft1 may be implicated in aging regulatory pathways. Here, we show that cells derived from hypomorph Ft1 mutant (Ft1(kof/kof)) mice exhibit telomeric defects and that Ft1(kof/kof) animals develop progeroid traits, including impaired growth, skeletal and skin defects, abnormal heart tissue, and sterility. We also demonstrate a genetic interaction between Ft1 and p53. The analysis of mice carrying mutations in both Ft1 and p53 (Ft1(kof/kof); p53(ko/ko) and Ft1(kof/kof); p53(+/ko)) showed that reduction in p53 rescues the progeroid traits of Ft1 mutants, suggesting that they are at least in part caused by a p53-dependent DNA damage response. Conversely, Ft1 reduction alters lymphomagenesis in p53 mutant mice. These results identify Ft1 as a new player in the aging process and open the way to the analysis of its interactions with other progeria genes using the mouse model.