tailieunhanh - Báo cáo khoa học: MBP-1 is efficiently encoded by an alternative transcript of the ENO1 gene but post-translationally regulated by proteasome-dependent protein turnover

Thec-myc promoter-binding protein-1 (MBP-1) is a transcriptional sup-pressor of tumorigenesis and thought to be the product of alternative translation initiation of the a-enolase (ENO1) transcript. In the present study, we cloned a 2552-bp novel cDNA with a putative coding sequence ofMBP-1and functionally examined its ability to encode the MBP-1 pro-tein. Similarly to ENO1, the obtained MBP-1was widely and differentially expressed in a variety of normal tissues and cancer cells. | ễFEBS Journal MBP-1 is efficiently encoded by an alternative transcript of the ENO1 gene but post-translationally regulated by proteasome-dependent protein turnover Jrhau Lung1 Ko-Jiunn Liu1 Jang-Yang Chang1 Sy-Jye Leu2 and Neng-Yao Shih1 1 National institute of Cancer Research NationalHealth Research Institutes Tainan Taiwan 2 Department of Microbiology and Immunology Taipei MedicalUniversity Taiwan Keywords alternative transcription initiation a-enolase c-myc promoter-binding protein-1 protein stability ubiquitination Correspondence . Shih National institute of Cancer Research NationalHealth Research Institutes Tainan 704 Taiwan Fax 886 6 208 3427 Tel 886 6 700 0123 ext. 65108 E-mail jshih@ or . Liu Department of Microbiology and Immunology Taipei MedicalUniversity Taipei 110 Taiwan Fax 886 2 2377 862 Tel 886 2 2736 1661 ext. 3414 E-mail cmbsycl@ Received 28 June 2010 revised 16 August 2010 accepted 19 August 2010 doi The c-myc promoter-binding protein-1 MBP-1 is a transcriptional suppressor of tumorigenesis and thought to be the product of alternative translation initiation of the a-enolase ENO1 transcript. In the present study we cloned a 2552-bp novel cDNA with a putative coding sequence of MBP-1 and functionally examined its ability to encode the MBP-1 protein. Similarly to ENO1 the obtained MBP-1 was widely and differentially expressed in a variety of normal tissues and cancer cells. Experiments using MBP-1 promoter-driven luciferase reporter assays biochemical cell fractionation followed by RT-PCR detection of the cytoplasmic mRNA and transcription translation-coupled reactions consistently demonstrated that this novel transcript was alternatively transcribed from intron III of the ENO1 gene and was feasible for MBP-1 production. Hypoxia treatments significantly increased the transcriptional activation of the MBP-1 gene. Blocking the proteasomal degradation by MG132 stabilized the MBP-1 protein .