ABSTRACT
TMF/ARA160 is a Golgi-associated protein whose level is downregulated in solid tumors. TMF changes its subcellular localization on exposure of cells to stress cues, thereby, directing proteins, such as the key transcription factor, Stat3, to proteasomal degradation. Here, we show that enforced ectopic expression of HA-TMF in PC3 prostate carcinoma cells, which do not express Stat3, significantly attenuated the development and growth of xenograft tumors elicited by these cells in athymic mice. Immunohistochemical analysis revealed impaired angiogenesis and accelerated onset of apoptosis in the HA-TMF-expressing tumors. RNA expression profiling revealed the downregulation of several proangiogenic genes in HA-TMF-expressing xenografts. Among these were the interleukin-8 and interleukin-1beta genes, whose expression is controlled by nuclear factor-kB. The level of the nuclear factor-kB component, p65/RelA, was decreased in HA-TMF-expressing xenografts, and TMF was found to direct the ubiquitination and proteasomal degradation of p65/RelA in metabolically stressed PC3 clones. Taken together, our findings indicate that TMF/ARA160 is a regulator of key transcription factors under metabolic constraints, thereby affecting angiogenesis and progression of solid tumors, which are subjected to metabolic stress.
Subject(s)
DNA-Binding Proteins/physiology , Interleukin-1beta/genetics , Interleukin-8/genetics , Prostatic Neoplasms/prevention & control , Transcription Factors/physiology , Animals , Blotting, Western , DNA Primers/chemistry , Disease Progression , Down-Regulation , Flow Cytometry , Humans , Immunoenzyme Techniques , In Situ Nick-End Labeling , Interleukin-1beta/metabolism , Interleukin-8/metabolism , Male , Mice , Mice, Inbred BALB C , Mice, Nude , NF-kappa B/genetics , NF-kappa B/metabolism , Prostatic Neoplasms/genetics , Prostatic Neoplasms/pathology , Proteasome Endopeptidase Complex/metabolism , RNA, Messenger/genetics , RNA, Messenger/metabolism , RNA, Small Interfering/pharmacology , Reverse Transcriptase Polymerase Chain Reaction , STAT3 Transcription Factor/genetics , STAT3 Transcription Factor/metabolism , TATA Box , Transcription Factor RelA/genetics , Transcription Factor RelA/metabolism , Transplantation, Heterologous , UbiquitinationABSTRACT
We herein describe a novel protein encoded by a single exon in a single-copy conserved mammalian gene. This protein, termed TMF regulated nuclear protein (TRNP), was identified in a yeast "two-hybrid" screen in which the "BC box" containing protein-TMF/ARA160 served as a bait. TRNP is a basic protein which accumulates in an insoluble nuclear fraction in mammalian cells. It is 227 aa long in humans and chimps and 223 aa long in mice. Enforced expression of TRNP in cells that do not express this protein significantly increased their proliferation rate by enhancing their cell-cycle progression from the G0/G1 to the S phase. Like another proliferation promoting factor, Stat3, TRNP was directed to proteasomal degradation by TMF/ ARA160. Thus, the trnp gene encodes a novel mammalian conserved nuclear protein that can accelerate cellcycle progression and is regulated by TMF/ARA160.
