2.4) IHF
IHF, the Integration Host Factor was first discovered as an
essential factor for site-specific recombination of phage λ (Miller and
Friedman, 1980). Subsequent studies have shown that IHF can act as a
regulator, either transcriptionally repressing or activating targets
depending on the context (Arfin et al. , 2000). IHF is involved in
the control of many functions including DNA replication, recombination
and cell regulation (Friedman, 1988), as well as various metabolic
processes, and adaptive processes (Freundlich et al. , 1992; Arfinet al. , 2000; Reverchon et al. , 2021). IHF forms a
heterodimer with two subunits encoded by ihfA and ihfB and
is mainly found in Proteobacteria (Table 1 ) (Nashet al. , 1987). IHF is one of the major bacterial NAPs
whose intracellular concentration changes during bacterial growth,
increasing during the transition to the stationary phase (Azam and
Ishihama, 1999). IHF binds DNA with significant specificity,
nevertheless its binding specificity appears to depend on the intrinsic
structure of DNA rather than the base composition of the DNA (Swinger
and Rice, 2004; Liu, Ma and Xu, 2018). Binding of IHF can induce sharp
bends in DNA, up to 160° (Dhavan et al. , 2002). This could
facilitate long-range interactions and affect the DNA topology. It
should be noted that IHF and HU proteins are both members of the DNABII
family of DNA-binding proteins and are strikingly similar to each other
in sequence and in their unique structural fold (Prieto et al. ,
2012). In addition, they share some similar targets (Bonnefoy and
Rouvière‐Yaniv, 1992), but interact differently with the DNA and have
different roles (Prieto et al. , 2012).