Histone H1 interphase phosphorylation becomes largely established in G1 or early S phase and differs in G1 between T-lymphoblastoid cells and normal T cells

Abstract

BackgroundHistone H1 is an important constituent of chromatin, and is involved in regulation of its structure. During the cell cycle, chromatin becomes locally decondensed in S phase, highly condensed during metaphase, and again decondensed before re-entry into G1. This has been connected to increasing phosphorylation of H1 histones through the cell cycle. However, many of these experiments have been performed using cell-synchronization techniques and cell cycle-arresting drugs. In this study, we investigated the H1 subtype composition and phosphorylation pattern in the cell cycle of normal human activated T cells and Jurkat T-lymphoblastoid cells by capillary electrophoresis after sorting of exponentially growing cells into G1, S and G2/M populations.ResultsWe found that the relative amount of H1.5 protein increased significantly after T-cell activation. Serine phosphorylation of H1 subtypes occurred to a large extent in late G1 or early S phase in both activated T cells and Jurkat cells. Furthermore, our data confirm that the H1 molecules newly synthesized during S phase achieve a similar phosphorylation pattern to the previous ones. Jurkat cells had more extended H1.5 phosphorylation in G1 compared with T cells, a difference that can be explained by faster cell growth and/or the presence of enhanced H1 kinase activity in G1 in Jurkat cells.ConclusionOur data are consistent with a model in which a major part of interphase H1 phosphorylation takes place in G1 or early S phase. This implies that H1 serine phosphorylation may be coupled to changes in chromatin structure necessary for DNA replication. In addition, the increased H1 phosphorylation of malignant cells in G1 may be affecting the G1/S transition control and enabling facilitated S-phase entry as a result of relaxed chromatin condensation. Furthermore, increased H1.5 expression may be coupled to the proliferative capacity of growth-stimulated T cells.

Histone H5—chromatin interactions in situ are strongly modulated by H5 C‐terminal phosphorylation

“…In conclusion, the phosphorylation conditions used in our reconstitution experiments resulted in a balanced mixture of phosphorylated H5 molecules (Fig. 1B) in accordance with a typical average phosphorylation pattern present in exponentially growing cells containing multiple H1 subtypes (57, 58).…”

Lymphocyte Gene Expression Signatures from Patients and Mouse Models of Hereditary Hemochromatosis Reveal a Function of HFE as a Negative Regulator of CD8+ T-Lymphocyte Activation and Differentiation In Vivo

“…Besides the above described genes, a significant up regulation of the MHC class II genes HLA - DQB1 and HLA - DRB1 , as well as the histone cluster 1 gene HIST1H1e , was also observed in patients with a low CD8 phenotype, supporting the notion of an activation and cell cycle progression pattern of these cells [ 26 ].…”

Linker histone partial phosphorylation: effects on secondary structure and chromatin condensation

“…A direct consequence of the induction of β-structure could be a less efficient neutralization of the linker DNA, which would increase the exchange rate of linker histones and, thus, favor local chromatin relaxation ( 36 ). Several studies indicate that partial linker histone phosphorylation is necessary for replication, transcription and other cellular processes ( 22 – 25 ). Traditionally, the effects of phosphorylation have been explained by a decrease of the positive net charge associated with the incorporation of the phosphate groups ( 20 ).…”

“…Increasing evidence suggests that histone H1 phosphorylation is involved in chromatin relaxation during the cell-cycle ( 21 – 27 ). H1 phosphorylation during the S-phase has been suggested to be a pre-requisite for DNA replication ( 22 ). S172 phosphorylation of H1.5 and H1.2 colocalized at DNA replication and transcription sites ( 23 ).…”