Functional Analysis of Microphthalmia-associated Transcription Factor in Pigment Cell-specific Transcription of the Human Tyrosinase Family Genes

doi:10.1074/jbc.272.1.503

Functional Analysis of Microphthalmia-associated Transcription Factor in Pigment Cell-specific Transcription of the Human Tyrosinase Family Genes*

From the ^‡ Department of Applied Physiology and Molecular Biology, Tohoku University School of Medicine, Aoba-ku, Sendai, Miyagi 980-77 and
the ^§ Department of Dermatology, Akita University School of Medicine, Akita 010, Japan

^¶ To whom correspondence should be addressed. Tel.: 81-22-717-8117; Fax: 81-22-717-8118.

Abstract

Tyrosinase, tyrosinase-related protein-1 (TRP-1), and TRP-2 are the enzymes involved in melanin biosynthesis and are preferentially expressed in pigment cells. Their human gene promoters share the 11-base pair M box containing a CATGTG motif, which was shown here to be bound in vitro by microphthalmia-associated transcription factor (MITF). Transient cotransfection analysis showed that MITF overexpression increased the expression of a reporter gene under the control of the human tyrosinase or TRP-1 gene promoter but not the TRP-2 promoter. The promoter activation caused by MITF is dependent on each CATGTG motif of the distal enhancer element, the M box, and the initiator E box of the tyrosinase gene and the TRP-1 M box. Furthermore, a truncated MITF lacking the carboxyl-terminal 125 amino acid residues transactivated the tyrosinase promoter less efficiently than did MITF, suggesting that MITF's carboxyl terminus contains a transcriptional activation domain, but unexpectedly such a truncated MITF remarkably transactivated the TRP-2 gene promoter. These results suggest that MITF is sufficient to direct pigment cell-specific transcription of the tyrosinase and TRP-1 genes but not the TRP-2 gene.

Footnotes

↵* This work was supported in part by Grants-in-Aid for Encouragement of Young Scientists (to K.-i. Y.), for Developmental Scientific Research (to S. S.), and for Scientific Research (to S. S. and Y. T.) from the Ministry of Education, Science, and Culture of Japan. The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

The nucleotide sequence(s) reported in this paper has been submitted to the GenBank™/EMBL Data Bank with accession number(s) D10243[GenBank].
↵¹ The abbreviations used are:

DOPA

3,4-dihydroxyphenylalanine

TRP-1

tyrosinase-related protein-1

TRP-2

tyrosinase-related protein-2

bHLH

basic helix loop helix

MITF

microphthalmia-associated transcription factor

TDE

tyrosinase distal element

TPE

tyrosinase proximal element

GST

glutathione S-transferase

bp

base pair(s).
- Received July 9, 1996.
- Revision received August 30, 1996.