ABSTRACT
Neurofibromatosis type 1 (NF1) microdeletion is a large genomic deletion that embraces at least 11 continuous genes at human chromosome 17q11.2. To date, most of these genes' functions still remain undefined. In this study, we report an unknown cytokine receptor like molecule (p48.2) that is frequently deleted in patients with type-1 and type-2 NF1 microdeletions in the neurofibromin locus. The cloned gene has 1317 base pair long that encodes a 438aa intracellular protein. The gene was subsequently named p48.2 based on its predicted molecular weight. A typical fibronectin type III (FNIII) domain was identified in p48.2 between Arg(176) and Pro(261) in which a palindromic Arg-Gly-Asp (RGD) repeat plus a putative Trp-Ser-X-Trp-Ser (WSXWS) motif were found at the domain's C-terminus. p48.2 mRNAs were abundant in many tumor cell lines and normal human tissues and up-regulated in some freshly isolated lung cancer and leukemia cells. Interestingly, over-expression of p48.2 in human embryo kidney 293T cells could significantly cause G0/G1 arrest and prevented S phase entry. In contrast, repressing endogenous p48.2 gene expression by specific siRNA markedly reduced G0/G1 population. Importantly, over-expression of p48.2 could significantly up-regulate rather than down-regulate cyclin D1 and cyclin D3 expressions. We further showed that the induction of cyclin D1 expression was directly due to the activation of signal transducers and activators of transcription 3 (STAT3), but was independent of RAS/mitogen-activated protein kinase (RAS/MAPK) signaling pathway. Thus, p48.2 may represent a novel type of intracellular protein functioning as a negative regulator at the G0/G1 phase.
Subject(s)
Cell Cycle Proteins/genetics , Cell Cycle , Intracellular Space/metabolism , Receptors, Cytokine/genetics , Amino Acid Sequence , Animals , Base Sequence , Cell Cycle/genetics , Cell Cycle Proteins/chemistry , Cell Cycle Proteins/metabolism , Cell Line , Cloning, Molecular , Computational Biology , Cyclin D1/genetics , Cyclin D1/metabolism , Cyclin D3/genetics , Cyclin D3/metabolism , Down-Regulation/genetics , G1 Phase , Gene Expression Profiling , Gene Expression Regulation , Genome, Human/genetics , Humans , Mice , Molecular Sequence Data , Promoter Regions, Genetic/genetics , RNA, Small Interfering , Receptors, Cytokine/chemistry , Receptors, Cytokine/metabolism , Resting Phase, Cell Cycle , STAT3 Transcription Factor/metabolism , Sequence Homology, Amino Acid , Signal TransductionABSTRACT
AIM: Cytokine receptor-like factor 3 (CRLF3) is a novel gene cloned from K562 cell line. The aim of the current study is to observe CRLF3 expression and subcellular localization in 293T cells and to express and purify the CRLF3 fusion protein in E.coli. METHODS: The plasmid pCMV-myc-CRLF3 was transiently transfected into 293T cell. The expression and localization of CRLF3 protein was observed by immunostaining approach. CRLF3 was also cloned into pGEX-4T-1 vector. The GST-CRLF3 fusion protein was expressed in E.coli and purified by GST affinity chromatography. RESULTS: CRLF3 protein was highly expressed in transfected 293T cells. CRLF3 protein was distributed in both cytoplasm and cell membrane. The GST-CRLF3 fusion protein was expressed as a M(r) 74 000 protein and then successfully purified from E.coli cells. CONCLUSION: Overexpressed CRLF3 is a cytoplasmic protein that distributes in both cytoplasm and cell membrane in mammalian cells. The recombinant GST-CRLF3 fusion protein had been isolated and could be used for further antibody production and functional characterization.