gga-miR-26a targets NEK6 and suppresses Marek's disease lymphoma cell proliferation.

MicroRNA (miRNA) are a class of highly conserved, small noncoding RNA that emerge as key posttranscriptional regulators in various neoplastic transformations. Our previous study profiling the miRNA transcriptome in Marek's disease virus (MDV)-induced lymphoma revealed many novel and differentially expressed miRNA, including gga-miR-26a, which was downregulated in MDV-infected spleens of chickens. In this study, differential expression of gga-miR-26a between MDV-infected and noninfected spleens at 4, 7, 14, 21, and 28 d postinfection was analyzed by real-time PCR. The results showed gga-miR-26a were downregulated in MDV-infected spleens at cytolytic infection, latency, and tumor transformation phases. Subsequent cell proliferation assay revealed cell viability was lower in gga-miR-26a mimic transfection group than that in negative controls. Target genes of gga-miR-26a were identified by luciferase reporter gene assay. The results showed significant interaction between gga-miR-26a and Never In Mitosis Gene A (NIMA)-related kinase 6 (NEK6) gene. Subsequent gain of function experiment and Western blot assay showed that mRNA and protein levels of NEK6 were downregulated after gga-miR-26 mimic was transfected into MDV-transformed lymphoid cell line (MSB-1), indicating that NEK6 was modulated by gga-miR-26a. The expression of NEK6 showed a higher trend in MDV-infected samples including tumorous spleen and MD lymphoma from liver than that in noninfected controls. The results suggested that gga-miR-26a inhibited MSB-1 cell proliferation. Gga-miR-26a and its direct target, NEK6, might play important roles in MDV infection.