Proc Natl Acad Sci U S A. 2006 Oct 31;103(44):16448-53. Epub 2006 Oct 18.

RIG-G as a key mediator of the antiproliferative activity of interferon-related pathways through enhancing p21 and p27 proteins.

Xiao S, Li D, Zhu HQ, Song MG, Pan XR, Jia PM, Peng LL, Dou AX, Chen GQ, Chen SJ, Chen Z, Tong JH.

Source

Shanghai Institute of Hematology and State Key Laboratory of Medical Genomics, Rui Jin Hospital, Health Science Center, Chinese Academy of Sciences and School of Medicine, Shanghai Jiao Tong University, 197 Rui Jin Road II, Shanghai 200025, China.

Abstract

The RIG-G gene, originally isolated from an acute promyelocytic leukemia cell line NB4, codes for a 60-kDa cytoplasmic protein that is induced by all-trans retinoic acid (ATRA) treatment along with the induction of morphological differentiation of NB4 cells. Here, we provide evidence that ectopic expression of Rig-G in U937 cells can lead to a significant accumulation of cells at G(1)/S transition. Growth arrest seems to occur by modulating several major cell cycle regulatory players. Interestingly, Rig-G alters JAB1 cellular distribution through interacting with this protein and increases the intracellular level of p27 by preventing it from the JAB-1-dependent and ubiquitin/proteasome-mediated degradation. Furthermore, we demonstrate a role of Rig-G for c-myc down-regulation that results in an up-regulation of p21, tightly associated with cell cycle arrest. In addition, our studies reveal that Rig-G is a direct target of STAT1, a key transcription factor in regulating IFN responses, and may be one of the first experimentally proven molecular mediators for the antiproliferative effect of IFN-alpha. Considering that IFN-alpha and ATRA synergistically inhibit growth along the intracellular pathways triggered by the two compounds in many cell types, we suggest that Rig-G may also represent one of the key molecular nodes of signaling cross-talk between ATRA and IFN-alpha.