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The soluble guanylyl cyclases (sGC), the receptor for nitric oxide, are hete-rodimers consisting of ana- and b-subunit. This study aimed to investigate the translational mechanism of the sGC b2-subunit. Two mRNA species for sGC b2 were isolated from human kidney. | ễFEBS Journal An internal ribosome entry site mediates the initiation of soluble guanylyl cyclase p2 mRNA translation Roberto I. Vazquez-Padron1 Si M. Pham1 Dania Mateu1 Sheik Khan1 and Abdelouahab Aitouche2 1 University of Miami Miller Schoolof Medicine FL USA 2 NationalInstitutes of Health Bethesda MD USA Keywords IRES nitric oxide soluble guanylyl cyclase translation untranslated region Correspondence R. I. Vazquez-Padron Division of Cardiothoracic Surgery and Vascular Biology Institute University of Miami Miller School of Medicine 1600 NW 10th Avenue RMSB 1063 Miami FL 33136 USA Fax 1 305 243 5636 Tel 1 305 243 1154 E-mail rvazquez@med.miami.edu Received 18 January 2008 revised 8 May 2008 accepted 13 May 2008 doi 10.1111 j.1742-4658.2008.06505.x The soluble guanylyl cyclases sGC the receptor for nitric oxide are heterodimers consisting of an a- and b-subunit. This study aimed to investigate the translational mechanism of the sGC b2-subunit. Two mRNA species for sGC b2 were isolated from human kidney. These transcripts had dissimilar 5 -untranslated regions 5 -UTRs . The most abundant sGC b2 mRNA showed numerous upstream open reading frames ORFs and stable secondary structures that inhibited in vivo and in vitro translation. To evaluate whether these 5 -UTRs harbored an internal ribosome entry site IRES that allows translation by an alternative mechanism we inserted these regions between the two luciferase genes of a bicistronic vector. Transfection of those genetic constructs into HeLa cells demonstrated that both sGC b2 leaders had IRES activity in a cell-type dependent manner. Finally the secondary structural model of the sGC b2 5 -UTR predicts a Y-type pseudoknot that characterizes the IRES of cellular mRNAs. In conclusion our findings suggest that sGC b2 5 -UTRs have IRES activity that may permit sGC b2 expression under conditions that are not optimal for scanning-dependent translation. The soluble guanylyl cyclases sGCs are the only receptors for nitric .
