Histones

• They are a protein family which associate themselves with nuclear eukaryotic DNA, forming nucleosomes. Being positively charged (alkaline character) by the amino acids they are made of, allows them to bond with DNA. Histones play an important role in gene regulation since they can suffer modifications post-translating (methylation, acetylation, phosphorylation, etc.) and in DNA winding (chromatin), allowing DNA to fit in the nucleus.

 

• Histones are rich in lysine and arginine and water-soluble. They are synthesized in the cytoplasm and posteriorly transported to the nucleus.

 

• There are 5 classes: H1 or H5 (superior molecular weight and responsible for the solenoid organization), H2A and H2B (rich in lysine), H3 and H4 (rich in arginine). Two copies of each histone H2A, H2B, H3 and H4, constitute a histone octamer, around which a DNA segment is wrapped around. This complex, associated with a H1 histone constitutes a nucleosome.

 Biologia Aplicada | 2013/2014 | Genes e Genomas | PL4 | Grupo 1

Duarte Oliveira A70097 | Filipe Rodrigues A68845 | João Ribeiro A68856 | José Miguel Sousa A68844 | Pedro Alves A69553