RESUMO
Sophisticated gene-regulatory mechanisms probably evolved in prokaryotes billions of years before the emergence of modern eukaryotes, which inherited the same basic enzymatic machineries. However, the epigenomic landscapes of eukaryotes are dominated by nucleosomes, which have acquired roles in genome packaging, mitotic condensation and silencing parasitic genomic elements. Although the molecular mechanisms by which nucleosomes are displaced and modified have been described, just how transcription factors, histone variants and modifications and chromatin regulators act on nucleosomes to regulate transcription is the subject of considerable ongoing study. We explore the extent to which these transcriptional regulatory components function in the context of the evolutionarily ancient role of chromatin as a barrier to processes acting on DNA and how chromatin proteins have diversified to carry out evolutionarily recent functions that accompanied the emergence of differentiation and development in multicellular eukaryotes.
Assuntos
Montagem e Desmontagem da Cromatina , DNA/genética , Genoma , Nucleossomos/genética , Transcrição Gênica , Animais , Evolução Biológica , Proteínas Cromossômicas não Histona/genética , Proteínas Cromossômicas não Histona/história , Proteínas Cromossômicas não Histona/metabolismo , DNA/história , DNA/metabolismo , Células Eucarióticas/citologia , Células Eucarióticas/metabolismo , Genômica/métodos , Histonas/genética , Histonas/história , Histonas/metabolismo , História do Século XXI , História Antiga , Humanos , Nucleossomos/química , Nucleossomos/metabolismo , Células Procarióticas/citologia , Células Procarióticas/metabolismo , Fatores de Transcrição/genética , Fatores de Transcrição/história , Fatores de Transcrição/metabolismoRESUMO
Polycomb (PcG) and Trithorax (TrxG) group proteins are evolutionarily conserved chromatin-modifying factors originally identified as part of an epigenetic cellular memory system that maintains repressed or active gene expression states. Recently, they have been shown to globally control a plethora of cellular processes. This functional diversity is achieved by their ability to regulate chromatin at multiple levels, ranging from modifying local chromatin structure to orchestrating the three-dimensional organization of the genome. Understanding this system is a fascinating challenge of critical relevance for biology and medicine, since misexpression or mutation of multiple PcG components, as well as of TrxG members of the COMPASS family and of the SWI/SNF complex, is implicated in cancer and other diseases.
