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Telomerase activity is constitutively expressed in the murine CD8+ T lymphocytes and controlled transcriptionally and post-translationally

Telomerase activity is constitutively expressed in the murine CD8+ T lymphocytes and controlled transcriptionally and post-translationally
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대학원 분자생명과학부
이화여자대학교 대학원
Telomerase는 염색체 말단 telomere의 반복구조를 합성할 수 있는 ribonucleoprotein enzyme으로서 정상 체세포, transformed된 세포, 그리고 germline 계열의 세포의 분열 능력 결정에서의 역할에 대해 주목 받고 있다. 정상 체세포가 telomerase 활성이 없는 반면에, 정상 임파구는 세포발달과 활성화 과정동안, transformed된 세포에서 나타나는 것과 비슷한 정도의 telomerase 활성을 가지는 것으로 보고 되어 왔으며, 이는 임파구 클론의 확장능력을 유지하는데 기여하는 것으로 생각된다. 본 연구에서는 생쥐의 T 임파구에서의 telomerase 활성조절을 살펴보기 위해, 먼저 생쥐의 CD8 양성 T 임파구 클론과 생쥐에서 분리한 nai¨ve CD8 양성 T 임파구의 telomerase 활성을 측정한 결과, 생쥐의 CD8 양성 T 임파구는 활성상태와 비활성 상태 모두에서 telomerase 활성을 나타냈다. 다음으로 telomerase의 catalytic subunit인 TERT 단백질의 세포내 발현 정도를 측정하여, telomerase 활성의 증가가 TERT 단백질 발현의 증가에 완전히 의존하지는 않는다는 사실을 알 수 있었다. 또한, telomerase 활성이 단백질 인산화 효소 억제제 처리로 감소되는 것을 관찰함으로써 telomerase 활성화가 인산화를 막음으로써 억제된다는 것을 보여주었다. 이 결과를 통해, 생쥐의 T 임파구는 telomerase 활성을 항시 가지고 있으며 이 telomerase 활성 조절을 위해 유전자 전사 조절과 단백질 발현 후 조절을 모두 이용함을 알 수 있다.;Telomerase, a ribonucleoprotein enzyme capable of synthesizing telomeric repeats, attracts attention for its possible role in determining the replicative capacity of normal somatic cells, transformed cells, and cells of the germline lineage. Differently from normal somatic cells with no telomerase activity, normal lymphocytes has been reported to have telomerase activity comparable to that found in transformed cells during development and activation, which substantiate a role in supporting the capacity of lymphocytes for extensive clonal expansion. Here, to define the telomerase regulation in murine T lymphocytes, telomerase activity in cloned murine CD8^(+) T cells and nai¨ve CD8^(+) T cells isolated from C57BL/6 mice was examined. It was demonstrated that telomerase activity is expressed in an unactivated state as well as in an activated state in the murine CD8^(+) T lymphocytes by using TRAP (telomeric repeats amplification protocol) assay. Next, the regulatory mechanism of telomerase activity at transcriptional and post-translational levels was investigated. By determining the expression level of the TERT (telomerase reverse transcriptase) protein, a key component for telomerase activity, it was observed that Increase of telomerase activity was partially dependent on the net increase of TERT expression, Also, telomerase activity was decreased after treatment with protein kinase inhibitors, indicating that telomerase activation was prevented by inhibition of phosphorylation. Therefore, these results suggest that telomerase activity is constitutively expressed in the murine resting T lymphocytes and controlled by both transcriptional regulation and post-translational modifications.
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