Chromatin remodelling complexes, including ISWI (Imitation SWI), NURF (Nucleosome remodelling Factor), and CHRAC (Chromatin Accessibility Complex), are key players in regulating gene expression and maintaining the structure of chromatin. Each has distinct functions and mechanisms of action in chromatin remodelling. ISWI is a member of the ATP-dependent chromatin remodelling complex family. Its primary function is to facilitate the movement of nucleosomes along DNA, leading to changes in chromatin structure. ISWI complexes are therefore involved in various processes, including transcriptional regulation, DNA repair, and heterochromatin formation. For the latter process, ISWI complexes often interact with heterochromatin-associated proteins, such as HP1 (Heterochromatin Protein 1). HP1 binds to histone H3 lysine 9 trimethylation (H3K9me3), a hallmark of heterochromatin. ISWI complexes, in conjunction with HP1 and other factors, contribute to the establishment and maintenance of heterochromatin by promoting the compaction of nucleosomes and the spreading of repressive histone modifications. ISWI complexes use energy derived from ATP hydrolysis to slide, reposition, or remove nucleosomes along the DNA. This action can create nucleosome-free regions, making DNA more accessible to transcription factors and other regulatory proteins. ISWI remodellers are also involved in spacing nucleosomes at regular intervals, contributing to chromatin compaction and stability. NURF is another ATP-dependent chromatin remodelling complex, and its primary function is also to alter nucleosome positioning to regulate gene expression. NURF plays a critical role in transcriptional activation, particularly in the context of development and differentiation. NURF contains multiple subunits, including a catalytic ATPase subunit (ISWI) and other accessory proteins. NURF recognizes specific DNA sequences or histone modifications, allowing it to target specific genomic regions. By using ATP hydrolysis, NURF can also reposition nucleosomes to expose or hide regulatory elements such as promoters and enhancers. This remodelling activity is essential for facilitating the binding of transcription factors and RNA polymerase to their target sites, thus promoting gene expression. CHRAC is another ATP-dependent chromatin remodelling complex that primarily functions in nucleosome assembly and disassembly. It plays a role in ensuring proper nucleosome spacing and maintenance of chromatin integrity, particularly during the processes of DNA replication and repair. CHRAC is composed of several subunits, including a catalytic ATPase subunit (ACF1 or CHRAC15) and other accessory proteins. CHRAC participates in nucleosome assembly by facilitating the deposition of histones onto newly synthesized DNA during replication. It also helps disassemble nucleosomes during processes like DNA repair. CHRAC complexes use ATP hydrolysis to create transient gaps in chromatin, allowing histone exchange or removal and ensuring proper DNA accessibility for replication and repair factors. Thus, ISWI, NURF, and CHRAC are distinct chromatin remodelling complexes with overlapping functions and mechanisms of action in regulating chromatin structure and gene expression. ISWI primarily focuses on nucleosome sliding and positioning, contributing to gene regulation and chromatin compaction. NURF, on the other hand, is important for nucleosome repositioning, especially during transcriptional activation, whilst CHRAC is involved in nucleosome assembly and disassembly during DNA replication and repair. Explore our full ISWI, NURF and CHRAC product range below and discover more, for less.