Translin-associated Factor X Is Post-transcriptionally Regulated by Its Partner Protein TB-RBP, and Both Are Essential for Normal Cell Proliferation

• Published in: The Journal of biological chemistry 2004-03, Vol.279 (13), p.12605-12614
• Main Authors: Yang, Shicheng, Cho, Yoon Shin, Chennathukuzhi, Vargheese M., Underkoffler, Lara A., Loomes, Kathleen, Hecht, Norman B.
• Format: Article
• Language: English
• Subjects: Animals; Blotting, Northern; Blotting, Western; Carrier Proteins - biosynthesis; Carrier Proteins - chemistry; Carrier Proteins - physiology; Cell Cycle; Cell Division; Cells, Cultured; DNA-Binding Proteins - biosynthesis; DNA-Binding Proteins - chemistry; DNA-Binding Proteins - physiology; Dose-Response Relationship, Drug; Embryo, Mammalian - cytology; Fibroblasts - metabolism; Flow Cytometry; HeLa Cells; Heterozygote; Humans; Kinetics; Leucine - chemistry; Mice; Mice, Transgenic; Microscopy, Fluorescence; NIH 3T3 Cells; Nuclear Proteins - biosynthesis; Nuclear Proteins - chemistry; Nuclear Proteins - physiology; Plasmids - metabolism; Protein Binding; Protein Structure, Tertiary; RNA Interference; RNA Processing, Post-Transcriptional; RNA, Messenger - metabolism; RNA-Binding Proteins; TB-RBP protein; Time Factors; Transfection; Transgenes; Translin-associated factor X; Ubiquitin - chemistry; Ubiquitin - metabolism
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M313133200

To determine the functions of the DNA/RNA-binding protein TB-RBP in somatic cells, we examined cultured primary mouse embryonic fibroblasts (MEFs) derived from TB-RBP-deficient mice. The TB-RBP-deficient MEFs exhibit a reduced growth rate compared with MEFs from littermates. Reintroduction of TB-RBP remedies this defect. A partner protein of TB-RBP, Translin-associated factor X (TRAX), was absent in TB-RBP-deficient MEFs, despite normal TRAX mRNA levels. TRAX is dependent upon the presence of TB-RBP and is removed from null MEFs following ubiquitination. Re-introduction of TB-RBP, but not TB-RBP lacking an oligomerization domain, into null MEFs stabilized TRAX protein without changing TRAX mRNA levels. The coordinated expression of TB-RBP and TRAX is also seen in synchronized cells, where the amount of TRAX protein but not TRAX RNA closely parallels TB-RBP levels throughout the cell cycle. In transgenic mice overexpressing TRAX in testis, total TB-RBP and TRAX levels are constant with reductions of endogenous TRAX compensating for exogenous TRAX. Using RNA interference, reductions of either TB-RBP or TRAX (without affecting TB-RBP) slow cell growth rates. We conclude that TRAX is post-transcriptionally stabilized by TB-RBP and both proteins are needed for normal cell proliferation.