The pulsatile nature of gene activity has recently emerged as a general property of the transcriptional process. It has been shown that the frequency and amplitude of transcriptional bursts can be subjected to extrinsic regulation. Here we have investigated if these parameters were constant throughout the cell cycle using the single molecule RNA FISH technique. We found evidence of transcriptional spikes upon mitotic exit in three different human cell lines. Recording of cell growth prior to hybridization and immuno-RNA FISH analysis revealed that these spikes were short-lived and subsided before completion of cytokinesis. The transient post-mitotic increase in transcriptional output was found to be the result of cells displaying a higher number of active alleles and/or an increased number of nascent transcripts per active allele, indicating that both the burst fraction and the amplitude of individual bursts can be increased upon mitotic exit. Our results further suggest that distinct regulatory mechanisms are at work shortly after mitotic exit and during the rest of interphase. We speculate that transcriptional spikes are associated with chromatin decondensation, a hallmark of post-mitotic cells that might alter the dynamics of transcriptional regulators and effectors.

• MeSH
• Alleles MeSH
• Cell Line MeSH
• Cell Cycle MeSH
• Hep G2 Cells MeSH
• Antigens, CD genetics   isolation & purification   MeSH
• DNA-Directed RNA Polymerases genetics   isolation & purification   MeSH
• Transcription, Genetic * MeSH
• In Situ Hybridization, Fluorescence methods   MeSH
• Humans MeSH
• Mitosis genetics   MeSH
• Receptors, Transferrin genetics   isolation & purification   MeSH
• RNA genetics   MeSH
• Single Molecule Imaging methods   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Antigens, CD MeSH
• CD71 antigen MeSH Browser
• DNA-Directed RNA Polymerases MeSH
• POLR2A RNA polymerase, human MeSH Browser
• Receptors, Transferrin MeSH
• RNA MeSH