Assembly and functions of heterochromatin in the fission yeast genome

In eukaryotic genomes, heterochromatin regulates various chromosomal processes including suppression of transcription and illegitimate recombination as well as proper segregation of chromosomes during cell division. Recent studies using the fission yeast Schizosaccharomyces pombe model system have revealed a complex interplay among RNA polymerase II transcription, RNAi machinery, and factors involved in posttranslational modifications of histones that are critical for the assembly and maintenance of heterochromatin. Heterochromatin proteins targeted to specific sites in the genome can spread across extended chromosomal domains and mediate epigenetic genome control by providing a recruitment platform for various factors including chromatin-modifying activities. In this chapter, we discuss mechanisms of heterochromatin assembly in fission yeast and highlight emerging evidence suggesting the involvement of heterochromatin factors in the suppression of noncoding RNAs across the genome.

Comparison of ELISA and HPLC for the determination of histamine in cheese

A competitive direct enzyme-linked immunosorbent assay (CD-ELISA) for histamine in cheese was compared with a reversed-phase liquid chromatography (RP-HPLC) method. Cheese was homogenized with phosphate-buffered saline (PBS), centrifuged, and filtered, and the supernatant was diluted with PBS for CD-ELISA. For RP-HPLC, biogenic amines (histamine, tyramine, putrescine, and cadaverine) were derivatized with 9-fluorenylmethylchloroformate, followed by reversed-phase chromatography and fluorescence detection. Detection limits and mean recoveries (10-1000 mg/kg) were 2 mg/kg and 93% for CD-ELISA and 1 mg/kg and 99% for RP-HPLC, respectively. Analysis of 50 commercial cheeses according to both methods showed good agreement for histamine (r = 0.979; concentration range = 2-1800 mg/kg). At a threshold level of 10 mg/kg, the ELISA gave no false-negative and three false-positive results. The results show that the ELISA is suitable for the determination of histamine in cheese.