Calyculin A Induces Premature Chromosome Condensation and Chromatin Compaction in G₁-Phase HeLa Cells without Histone H1 Phosphorylation.

ABSTRACT: We show here that treatment of HeLa cells with calyculin A, an inhibitor of Protein Phosphatases 1 and 2A, induces premature chromosome condensation (PCC) at any point in interphase of the cell cycle. Chromosomes in G₁-phase PCC closely resemble metaphase chromatids in the light microscope, and measurements using FLIM-FRET show that they have the same level of chromatin compaction as metaphase chromosomes. However, histone H1 is not phosphorylated in G₁- or early S-phase PCC. These results suggest that H1 phosphorylation is not required for mitotic chromosome condensation and chromatin compaction. They also confirm that Cdk1/cyclin B, which directly phosphorylates histone H1, is not active in G₁ and thus is not essential for G₁-PCC. We suggest th

SUBMITTER: Kochanova NY 

PROVIDER: S-EPMC12330644 | biostudies-literature | 2025 Jul

REPOSITORIES: biostudies-literature