Transcription of dbpA, a Y box binding protein, is positively regulated by E2F1: implications in hepatocarcinogenesis

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Abstract

Human hepatocellular carcinoma is one of the most common cancers in the world. We previously showed that dbpA, a member of the Y box family of proteins, could accelerate the process of inflammation-induced hepatocarcinogenesis, and that dbpA is more abundantly expressed in hepatocellular carcinoma than in non-tumorous tissue. In this study, to clarify the mechanism by which expression of dbpA is enhanced in the proliferative state, we examined the transcriptional activity of the dbpA promoter region. We focused on the sequence 5′-TTTGGGGC-3′ (−8 to −1 in the promoter region) resembling the E2F binding site (one base mismatch, TFSEARCH score 86.2). By overexpressing E2F1 in Huh-7 cells, transcriptional activity of dbpA was significantly increased, and this increase was abolished by mutating or deleting this sequence. Thus, expression of dbpA was positively regulated by E2F1, suggesting that one of the effects of E2F1 on cell proliferation might be mediated by dbpA at the carcinogenesis step.

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Materials and methods

Plasmid construction. The firefly luciferase expression vector was made by insertion of the synthesized DNA corresponding to the dbpA promoter region into pGL3-Basic vector (Promega). The DNAs were synthesized so that they contained the MluI and BglII recognition site at each end after annealing. They were digested with MluI and BglII, and ligated to the MluI–BglII digested pGL3-Basic vector. The synthetic DNAs covering −17 to +106 relative to the transcription start point (123 mer), −4 to +106

Decreased transcriptional activity of dbpA promoter region without the sequences resembling E2F binding site

As shown in Fig. 1, the sequence 5′-TTTGGGGC-3′ (−8 to −1) resembling the E2F binding element 5′-TTT(G/C)GCGC-3′ exists in the dbpA promoter region. In order to examine whether this sequence is important for the transcriptional activity of this promoter, we prepared reporter vectors containing this region with successive deletions, shown in Fig. 2A, and assayed their luciferase activity. Luciferase activity was highest with the vector containing the (−17 to +106) region, in which the 8-base

Discussion

The frequency of human HCC is dependent on the severity and duration of chronic inflammation of the liver, regardless of its etiology. We previously reported that dbpA, a member of the Y box binding protein family, could accelerate inflammation-induced hepatocarcinogenesis [8]. The finding of enhanced expression of dbpA in human HCC [8] and in regenerating mouse liver (Fig. 4) suggested that dbpA is a proliferation-associated protein, like YB-1, the prototype member of the same family [3], [4],

References (34)

  • Y. Ito et al.

    Y-box binding protein expression in thyroid neoplasms: its linkage with anaplastic transformation

    Pathol. Int.

    (2003)
  • K. Shibao et al.

    Enhanced coexpression of YB-1 and DNA topoisomerase II alpha genes in human colorectal carcinomas

    Int. J. Cancer

    (1999)
  • K. Kajino et al.

    Recombination hot spot of hepatitis B virus genome binds to members of the HMG domain protein family and the Y box binding protein family; implication of these proteins in genomic instability

    Intervirology

    (2001)
  • S. Kudo et al.

    Characterization of the gene for dbpA, a family member of the nucleic-acid-binding proteins containing a cold shock domain

    Eur. J. Biochem.

    (1995)
  • T. Heinemeyer et al.

    Databases on Transcriptional Regulation: TRANSFAC, TRRD, and COMPEL

    Nucleic. Acids. Res.

    (1998)
  • E.A. Conner et al.

    Dual functions of E2F1 in a transgenic mouse model of liver carcinogenesis

    Oncogene

    (2000)
  • P.L. Felgner et al.

    Lipofection: a highly efficient, lipid-mediated DNA-transfection procedure

    Proc. Natl. Acad. Sci. USA

    (1987)
  • Cited by (0)

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