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Biogenesis and cell cycle relationship of poly(A)- actin mRNA in mouse ascites cells
Abstract:
A variety of rapidly growing mammalian cells contain a substantial portion of their actin mRNA in a poly(A)- form. We have used DNA-driven hybridization of a cloned actin cDNA-containing plasmid with pulse-labeled RNA from mouse S-180 ascites cells to examine newly synthesized actin mRNA. Our results indicate that the same proportion of newly synthesized and steady-state actin mRNA (approx. 40%) exists in a poly(A)- deficient form. This suggests that the poly(A)- form arises by some process other than slow cytoplasmic de-adenylation of a poly(A)+ precursor. We have also examined cell cycle-enriched populations of S-180 ascites cells for the presence of poly(A)- actin mRNA. Results from these experiments indicate that cells in G1 phase of the cell cycle contain predominantly poly(A)+ actin mRNA, while the poly(A)- form is restricted to late-S and post-S phase cells.
Insights
Most mammalian actin messenger RNA (mRNA) exists without a poly(A) tail, suggesting a unique biogenesis pathway. This poly(A)- form is predominantly found in late-stage cell cycle phases.
Area of Science:
- Molecular Biology
- Cell Biology
- Biochemistry
Background:
- Rapidly growing mammalian cells exhibit a significant fraction of actin mRNA lacking a poly(A) tail.
- The functional implications and origin of this poly(A)- actin mRNA remain to be fully elucidated.
Purpose of the Study:
- To investigate the proportion and origin of poly(A)- actin mRNA in mammalian cells.
- To determine the cell cycle-specific distribution of poly(A)- actin mRNA.
Main Methods:
- DNA-driven hybridization using a cloned actin cDNA plasmid.
- Analysis of pulse-labeled RNA from mouse S-180 ascites cells.
- Examination of cell cycle-enriched populations.
Main Results:
- Approximately 40% of both newly synthesized and steady-state actin mRNA are poly(A)- deficient.
- The poly(A)- form of actin mRNA does not appear to result from slow cytoplasmic de-adenylation.
- Poly(A)+ actin mRNA is prevalent in G1 phase cells, while poly(A)- actin mRNA is concentrated in late-S and post-S phase cells.
Conclusions:
- The poly(A)- actin mRNA likely originates through a mechanism independent of cytoplasmic de-adenylation.
- Actin mRNA polyadenylation status is cell cycle-dependent, with distinct forms accumulating at specific stages.