title: Human dipeptidyl peptidase III mRNA variant I and II are expressed concurrently in multiple tumor derived cell lines and translated at comparable efficiency in vitro.
abstract: Dipeptidyl peptidase III (DPP III) is an emerging biomarker of human cancers. Expression, specificity, and function of human DPP III (hDPP III) mRNA variant I (V-I), II (V-II), and III (V-III) are poorly understood. Here, we investigated expression of these variants in multiple human tumor derived cell lines. DNA sequencing revealed concurrent expression of hDPP III V-I and V-II in U87MG (glioblastoma), SCC4 (squamous cell carcinoma), SiHa (carcinoma of uterus) cells. In SKOV1 cells, a cell line derived from ovarian carcinoma where a positive correlation between histological aggressiveness of the malignancy and hDPP III expression has previously been established, only V-II could be detected. Human DPP III V-III, which lacks an in-frame coding sequence, could not be detected in any of these cell lines. 5' untranslated region (UTR) of hDPP III V-II contains nucleotides GCA (-12 to -10 bp) upstream to the translation initiator codon (AUG). These nucleotides are absent from V-I and V-III, however, both V-I and V-II encode for the same hDPP III protein isoform-I. In vitro transcription coupled translation assay using hDPP III V-I and V-II expression vectors which contained full length V-I and V-II cDNA including the variable 5' UTR cloned under T7 promoter, respectively revealed a comparable translational efficiency for both the variants, abrogating involvement of nucleotides GCA (-12 to -10 bp) in translation of the variants. Our results, for the first time, demonstrate concurrent expression in multiple tumor derived cell lines and a comparable in vitro translational efficiency for hDPP III V-I and II.
authors.affiliation: Room No. 3009, Department of Biochemistry, All India Institute of Medical Sciences, New Delhi, 110029, India.
authors.forename: Subhash C
authors.initials: SC
authors.lastname: Prajapati
authors.affiliation: Room No. 3009, Department of Biochemistry, All India Institute of Medical Sciences, New Delhi, 110029, India. s_s_chauhan@hotmail.com.
authors.forename: Shyam S
authors.initials: SS
authors.lastname: Chauhan
mesh_terms: D045744:Cell Line, Tumor; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D014176:Protein Biosynthesis
chemical_list: D007527:Isoenzymes; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases; C539603:DPP3 protein, human
keywords: Arg–Arg β-naphthylamide; Cancer biomarker; DPP III; Glioblastoma; Translational efficiency; mRNA variants