Activation of the Long Terminal Repeat of Human Endogenous Retrovirus K by Melanoma-Specific Transcription Factor MITF-M

Autor: Iyoko Katoh, Anna Mírová, Shun-ichi Kurata, Yasushi Murakami, Kenji Horikawa, Natsuko Nakakuki, Takunobu Sakai, Kunihiko Hashimoto, Ayako Maruyama, Takaaki Yonaga, Nahoko Fukunishi, Kohji Moriishi, Hirohisa Hirai
Jazyk: angličtina
Rok vydání: 2011
Předmět:
Zdroj: Neoplasia: An International Journal for Oncology Research, Vol 13, Iss 11, Pp 1081-1092 (2011)
Druh dokumentu: article
ISSN: 1476-5586
1522-8002
DOI: 10.1593/neo.11794
Popis: The human and Old World primate genomes possess conserved endogenous retrovirus sequences that have been implicated in evolution, reproduction, and carcinogenesis. Human endogenous retrovirus (HERV)-K with 5′LTR-gag-pro-pol-env-rec/np9-3′LTR sequences represents the newest retrovirus family that integrated into the human genome 1 to 5 million years ago. Although a high-level expression of HERV-K in melanomas, breast cancers, and terato-carcinomas has been demonstrated, the mechanism of the lineage-specific activation of the long terminal repeat (LTR) remains obscure. We studied chromosomal HERV-K expression in MeWo melanoma cells in comparison with the basal expression in human embryonic kidney 293 (HEK293) cells. Cloned LTR of HERV-K (HML-2.HOM) was also characterized by mutation and transactivation experiments. We detected multiple transcriptional initiator (Inr) sites in the LTR by rapid amplification of complementary DNA ends (5′ RACE). HEK293 and MeWo showed different Inr usage. The most potent Inr was associated with a TATA box and three binding motifs of microphthalmia-associated transcription factor (MITF). Both chromosomal HERV-K expression and the cloned LTR function were strongly activated in HEK293 by transfection with MITF-M, a melanocyte/melanoma–specific isoform of MITF. Coexpression of MITF and the HERV-K core antigen was detected in retinal pigmented epithelium by an immunofluorescence analysis. Although malignant melanoma lines MeWo, G361, and SK-MEL-28 showed enhanced HERV-K transcription compared with normal melanocytes, the level of MITF-M messenger RNA persisted from normal to transformed melanocytes. Thus, MITF-M may be a prerequisite for the pigmented cell lineage–specific function of HERV-K LTR, leading to the high-level expression in malignant melanomas.
Databáze: Directory of Open Access Journals
Externí odkaz: