Proliferating cell nuclear antigen/cyclin is an interleukin 2-responsive gene

Area of Science:

• Immunology
• Cell Biology
• Molecular Biology

Background:

• A protein designated p36 is synthesized at high rates during interleukin 2 (IL-2)-driven T lymphocyte proliferation.
• p36 biosynthesis increases significantly during the mid-G1 phase of the cell cycle and remains elevated during proliferation.

Purpose of the Study:

• To identify the protein p36 and elucidate its role in T lymphocyte proliferation.
• To investigate the relationship between p36 expression and cell cycle progression.

Main Methods:

• Two-dimensional gel electrophoresis to compare p36 migration with known proteins.
• Immunoprecipitation using antiserum against proliferating cell nuclear antigen (PCNA)/cyclin.
• Indirect immunofluorescence to detect PCNA/cyclin localization and accumulation in T cells.

Main Results:

• p36 exhibits identical migration patterns to PCNA/cyclin on two-dimensional gels.
• Antiserum to PCNA/cyclin specifically immunoprecipitates p36.
• PCNA/cyclin accumulates in the nucleus of IL-2-stimulated T lymphocytes during proliferation.
• PCNA/cyclin is undetectable before the S phase and after proliferation ceases.

Conclusions:

• The protein p36 is identified as PCNA/cyclin.
• IL-2 induces PCNA/cyclin expression in T lymphocytes.
• PCNA/cyclin accumulation is tightly linked to T lymphocyte proliferation, suggesting a key regulatory role.