Abstract
Linker histone H1 is a fundamental chromatin component, essential for higher-order chromatin compaction and transcriptional regulation. Chromatin regulator associated with M phase protein 1 (CRAMP1) was recently identified as a highly conserved factor that promotes the transcription of both replication-dependent and replication-independent H1 variants. This review synthesizes evidence that CRAMP1-mediated H1 production is critical for development via epigenetic regulation. We further summarize the multifaceted roles of H1 in maintaining genome integrity by facilitating heterochromatin formation and by serving as a key suppressor of transposable elements from Drosophila to mammals. Finally, we discuss how post-translational modifications on H1 dynamically regulate its function in chromatin dynamics and the DNA damage response. Collectively, this overview positions H1 and its master regulator CRAMP1 as important players in chromatin organization, with emerging roles in development, genome defense, and disease.
