COLD SPRING HARBOR, N.Y. (Tues., Sept. 1, 2009) – Chromatin Immunoprecipitation (ChIP) is an invaluable method for studying the interactions between proteins and DNA on a genome-wide scale. ChIP can be used to determine whether a transcription factor interacts with a candidate target gene, and is used to monitor the presence of histones with posttranslational modifications at specific genomic locations. The results are often extremely useful for investigating the functions of specific transcription factors or histone modifications. In the September issue of Cold Spring Harbor Protocols (www.cshprotocols.org/TOCs/toc9_09.dtl), Michael Carey (http://portal.ctrl.ucla.edu/biological-chemistry/institution/personnel?personnel_id=45403), Craig Peterson (http://www.umassmed.edu/pmm/faculty/peterson.cfm), and Stephen Smale (http://dgsom.healthsciences.ucla.edu/institution/personnel?personnel_id=45693) present "Chromatin Immunoprecipitation (ChIP)," an optimized protocol for use in mammalian cells. The article is freely available on the website for Cold Spring Harbor Protocols (http://cshprotocols.cshlp.org/cgi/content/full/2009/9/pdb.prot5279).

Phage-based E. coli homologous recombination systems have been extensively developed in recent years, and these recombination-mediated genetic engineering ("recombineering") methods are now the preferred technique for carrying out genetic modifications in chromosomes and plasmids. Recombineering is efficient and precise and circumvents many of the problems of traditional genetic engineering methods, primarily the need to locate specific restriction enzyme sites. "Construction of Gene-Targeting Vectors by Recombineering," from Pentao Liu and colleagues at the Wellcome Trust Sanger Institute (http://www.sanger.ac.uk/Teams/faculty/liu/) gives detailed instructions for using recombineering to construct targeting vectors for the generation of conditional knockout mice. The article is freely accessible on the website for Cold Spring Harbor Protocols (http://cshprotocols.cshlp.org/cgi/content/full/2009/9/pdb.prot5291).