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The mitogen-regulated protein/proliferin transcript is degraded in primary mouse embryo fibroblast but not 3T3
U M Malyankar1, S R Rittling, A Connor
1Department of Biological Sciences, Rutgers University, Piscataway, NJ 08855.
Abstract:
An understanding of what changes occur in the control of gene expression when mammalian cells "spontaneously" immortalize is important to our knowledge of how cancer develops. We describe here an alteration in regulation that occurs when primary mouse embryo fibroblasts (MEFs) are immortalized according to a 3T3 regimen. Mitogen-regulated protein/proliferin mRNA is undetectable in northern blots of RNA from (mortal) MEFs, whereas it is readily detected in immortal 3T3 cell lines derived from the MEFs. Incompletely processed nuclear transcripts of the mitogen-regulated protein/proliferin gene can be detected in MEF RNA preparations by northern blotting and reverse transcriptase polymerase chain reaction analyses, although at roughly half the abundance observed in 3T3 cells. We hypothesize that some attribute of the primary unprocessed transcript determines its assignment to this unique degradative pathway. These results reveal that during passage of MEFs according to a 3T3 regimen the ability of the primary cells to suppress the expression of certain genes by degrading the nuclear transcript is lost concomitantly with immortalization.
Insights
Gene expression regulation changes during mammalian cell immortalization. Primary mouse embryo fibroblasts lose the ability to suppress gene expression, a process linked to cancer development.
Area of Science:
- Cell Biology
- Molecular Biology
- Genetics
Background:
- Understanding gene expression control during mammalian cell immortalization is crucial for cancer research.
- Spontaneous immortalization of cells involves alterations in gene regulation.
- Primary mouse embryo fibroblasts (MEFs) are a model for studying cellular aging and immortalization.
Purpose of the Study:
- To investigate changes in gene expression regulation during the immortalization of primary mouse embryo fibroblasts (MEFs) using the 3T3 regimen.
- To identify specific genes or transcripts affected during this process.
- To elucidate the mechanisms underlying altered gene expression in immortalized cells.
Main Methods:
- Northern blotting to detect mRNA levels.
- Reverse transcriptase polymerase chain reaction (RT-PCR) to analyze nuclear transcripts.
- Comparison of gene expression profiles between mortal MEFs and immortalized 3T3 cell lines.
Main Results:
- Mitogen-regulated protein/proliferin mRNA was undetectable in mortal MEFs but readily detected in immortal 3T3 cells.
- Incompletely processed nuclear transcripts of the mitogen-regulated protein/proliferin gene were found in MEFs at lower abundance than in 3T3 cells.
- The ability of primary cells to suppress gene expression via nuclear transcript degradation is lost during immortalization.
Conclusions:
- Mammalian cell immortalization via the 3T3 regimen is associated with a loss of suppression in gene expression.
- This loss of gene expression suppression is linked to the degradation pathway of nuclear transcripts.
- Further research is needed to identify the specific attributes of transcripts that determine their degradation pathway.