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Metabolism of polyadenylated mRNA in growing human lymphocytes
Abstract:
The kinetics of degradation of newly synthesized, cytoplasmic polyadenylated RNA have been examined in normal human lymphocytes stimulated to grow with phytohemagglutinin. A single class of poly(A)-bearing RNA was identified with a half-life of approximately 50 h. In the presence of actinomycin D, the half-life was 5 to 6 h, and virtually no decay of pulse-labeled material was detectable after 6 h of chase incubation with cordycepin. These findings contrast sharply with data obtained from other growing human cells used as controls: polyadenylated mRNA in MOLT-4 cells, a cultured line of T lymphocytes, had a half-life of 2 h in the presence of actinomycin D. The stability of poly(A)-containing RNA in stimulated lymphocytes from normal donors is therefore not simply a manifestation of cell proliferation. In normal resting lymphocytes, Berger and Copper [(1975) Proc. Natl. Acad. Sci. U.S. 72, 3873--3877] reported the existence of 2 classes of polyadenylated mRNA with half-lives of under an hour and greater than 20 h, respectively. Since short-lived poly(A)-bearing mRNA is absent from mitogen-stimulated lymphocytes, the data suggest that stabilization of previously labile poly(A)-bearing RNA is one of many carefully regulated processes accompanying growth induction in normal lymphoid cells.
Insights
Stimulated human lymphocytes stabilize their polyadenylated RNA, showing a half-life of 50 hours. This contrasts with resting cells and suggests regulated RNA stabilization during growth induction.
Area of Science:
- Molecular Biology
- Cell Biology
- Immunology
Background:
- Cytoplasmic polyadenylated RNA plays a crucial role in gene expression.
- Understanding RNA kinetics is vital for comprehending cellular regulation.
- Lymphocyte activation involves complex molecular changes, including RNA processing.
Purpose of the Study:
- To investigate the degradation kinetics of newly synthesized polyadenylated RNA in phytohemagglutinin-stimulated human lymphocytes.
- To compare RNA stability in stimulated lymphocytes with other human cell types and resting lymphocytes.
- To determine if RNA stabilization is a regulated process during lymphoid cell growth induction.
Main Methods:
- Examining the degradation kinetics of cytoplasmic polyadenylated RNA in normal human lymphocytes.
- Utilizing phytohemagglutinin to stimulate lymphocyte growth.
- Employing actinomycin D and cordycepin to inhibit RNA synthesis and assess RNA decay.
- Comparing RNA half-lives in stimulated lymphocytes with control cell lines (MOLT-4) and previously reported data on resting lymphocytes.
Main Results:
- A single class of poly(A)-bearing RNA with a half-life of approximately 50 hours was identified in stimulated lymphocytes.
- In the presence of actinomycin D, the RNA half-life decreased to 5–6 hours.
- Short-lived poly(A)-bearing mRNA, present in resting lymphocytes, was absent in mitogen-stimulated lymphocytes, indicating stabilization.
Conclusions:
- The stability of poly(A)-containing RNA in stimulated lymphocytes is not solely due to cell proliferation.
- Mitogen stimulation leads to the stabilization of previously labile poly(A)-bearing RNA.
- This stabilization is a regulated process accompanying growth induction in normal lymphoid cells.