Biology Reference
In-Depth Information
4.1.1. FurA - a regulator of global transcription?
At the transcriptional level, FurA of
Anabaena
sp. PCC 7120 is autoregulated,
as established for
Anabaena
sp
.
PCC 7119 (
Hernández, López-Gomollón
et al., 2006
), and likely modulated by FurB and FurC. The latter was con-
cluded from the observed strong binding of FurB and the weak binding of
FurC to the promoter region of FurA (
Hernández, López-Gomollón et al.,
2004
). The activity is influenced by manganese and the redox state of the
environment (
Hernández, López-Gomollón et al., 2006
), the latter influ-
encing the oligomerization state of the protein (
Lostao, Peleato, Gómez-
Moreno, & Fillat, 2010
). FurA regulated genes were analysed in strains with
enhanced FurA content either by disrupting the sRNA (
Hernández, Muro-
Pastor et al., 2006
) or by placing
furA
behind a copper-inducible promoter
(Gonzales et al., 2010). The latter mutant shows a fragmentation pheno-
type as previously identified for strains with defects in the outer membrane
integrity or septosome formation (
Bauer, Buikema, Black, & Haselkorn,
1995
;
Flores et al., 2007
;
Nicolaisen, Mariscal et al., 2009
;
Wilk et al., 2011
).
This is consistent with the observed FurA-dependant regulation of the
outer membrane TBDT SchT (González et al., 2010).
Enhanced levels of FurA are found to reduce the expression of genes cod-
ing for the DNA-binding protein A from stationary phase DpsA (alr3808;
Hernández et al., 2007
), the 11-kDa protein of PSII PsbZ (all1258), the
iron-containing superoxide dismutase SodB (alr2938), the thiol peroxidases
GCT1 (alr3183) and GCT3 (all2375; Gonzales et al., 2010), peroxiredoxins
(alr4641; all1541), the thioredoxin reductase TrxB (all0737), the modula-
tors of DNA gyrase TldD (all5219) and PmbA (all5218), the protease Abp1
(all1940), the succinate-semialdehyde dehydrogenase (all3556) and the
two-component regulator OrrA (alr3768; Gonzales et al., 2011). Confirm-
ing a FurA regulation by repression, FurA was found to physically interact
with almost all of the promoter regions of the according genes (González
et al., 2010, 2011). Remarkably, several genes upregulated in FurA expres-
sion strains have been identified as well. Among those are genes coding
for the PSI components such as PsaA (alr5154) and PsaB (alr5155), for
the PSII component PsbB (all0138), for the manganese-containing super-
oxide dismutase SodA (alr2938), for the bacterial actins MreB and MreC
(all0087; all0086), for the IsiA protein (all4001), for the outer membrane
TBDT SchT (alr0397; Gonzales et al., 2010), for the thiamine biosynthe-
sis protein ThiC (all0982) and the CO
2
concentrating mechanism protein
CcmM (all0865; Gonzales et al., 2011). Thus, one could speculate that FurA
not only is involved in expression repression under normal conditions but
