Epigenetic regulation of development by histone lysine methylation.

Epigenetic mechanisms contribute to the establishment and maintenance of cell-type-specific gene expression patterns. In this review, we focus on the functions of histone lysine methylation in the context of epigenetic gene regulation during developmental transitions. Over the past few years, analysis of histone lysine methylation in active and repressive nuclear compartments and, more recently, genome-wide profiling of histone lysine methylation in different cell types have revealed correlations between particular modifications and the transcriptional status of genes. Identification of histone methyltransferases (HMTases) and specific binding factors for most methylated lysine positions has provided a novel insight into the mechanisms of epigenetic gene regulation. In addition, analyses of HMTase knockout mice show that histone lysine methylation has important functions for normal development. In this study, we review mechanisms of gene activation and repression by histone lysine methylation and discuss them in the context of the developmental roles of HMTases.

Characterization of recombinant cytokine fragments using isotachophoresis-capillary zone electrophoresis, reversed-phase high performance liquid chromatography, and mass spectrometry.

PURPOSE: Capillary zone electrophoresis with isotachophoretic sample preconcentration (ITP-CZE) and reversed-phase high performance liquid chromatography (RP-HPLC) with UV detection and on-line coupling to electrospray-ionization mass spectrometry were investigated for their potential to separate and identify fragments of recombinant human interleukin-6 formed during acidic stress of the parent protein. RESULTS: Based on the orthogonal separation principles governing ITP-CZE and RP-HPLC, different peak patterns were observed using both methods. The selectivity of ESI-MS allowed identification of several co-migrating compounds. Data obtained by on-line ESI-MS were compared to results from off-line investigations by MALDI-TOF-MS performed with single fractions collected from the RP-HPLC system. Cleavage of the protein backbone occurred preferably at acid-labile Asp-sites. The total amount of rhIL-6 needed for ITP-CZE-ESI-MS identification of all fragments was only in the upper femtomole range, while RP-HPLC required amounts of protein three orders of magnitude higher. On the other hand, the low CE sample volume opposes the collection of fractions to perform off-line analysis. CONCLUSIONS: Growing acceptance of CE with on-line MS detection for pharrmaceutical quality control of proteins is expected.