Geoscience Reference
In-Depth Information
tBp-containing
and tBp-free-
containing
complexes
implicated in
transcription
A number of distinct multi-protein complexes containing TBP-
associated factors, but lacking TBP, were found in cells from
different organisms. The complexes such as TBP-free TAF-
containing complex (TFTC), TFTC-related PCAF/GCN5 com-
plexes, Spt-Ada-Gcn5 acetyltransferase (SAGA), SAGA-like
complex (SLIK), Spt3-TAF9-GCN5L acetylase (STAGA) and
polycomb complex 1 (PRC1) possess multiple and essential
functions in the general transcription regulation of RNA POL II
genes (Thomas and Chiang, 2006; Baumann et al., 2010). These
complexes are implicated in gene activation mainly due to their
histone acetyltransferase (HAT) activity and co-activator func-
tion of TAFs, whereas PRC1 is implicated in gene silencing
(Garrick et al., 2008). Although much information about these
complex components in yeast, human and metazoan species is
available, there is little information in the case of plants. Yeast
and human SAGA complexes are encompassed by 20 sub-
units with a total mass of approximately 1.8 MDa (Rodriguez-
Navarro, 2009). SAGA complex is involved in 10% RNA Pol
II-dependent transcriptional regulation of yeast genes (Bhaumik,
2011). Components of the SAGA complex are also studied in the
plant in light, abiotic and biotic stress conditions. SAGA com-
plex regulating gene expression responds to environmental stress
conditions (Baker and Grant, 2007). Many reports suggest that
SAGA complex is directly or indirectly involved in many devel-
opments and stress-induced signalling pathways, for instance,
UV induced (Pankotai et al., 2005), high osmotic stress induced
(Zapater et al., 2007) and arsenite stress condition (Nagy et al.,
2009). Huisinga and Pugh (2004) also reported that the SAGA
complex of
S. cerevisiae
is involved in the up-regulation of genes
in response to environmental stresses including carbon starva-
tion (Huisinga and Pugh, 2004).
Arabidopsisada2b-1
mutants
display more hypersensitivity to salt stress (Hark et al., 2009;
Kaldis et al., 2011) and ABA stress than wild-type plants (Hark
et al., 2009). Although
sgf29a
mutant shows salt tolerance, the
gene expression level of some stress-related genes was reduced
in
sgf29a
mutant such as RD29b (responsive to desiccation 29b),
RAB18 (responsive to aba 18) and COR78 (cold-regulated 78)
(Kaldis et al., 2011).
Arabidopsis
GCN5 and ADA2b proteins
show a role in cold acclimation and mutations in these proteins
display the reduction of cold-inducible COR gene expression
(Stockinger et al., 2001; Vlachonasios et al., 2003; Mao et al.,
2006; Hark et al., 2009). Thus, the characteristics of the SAGA
complex in regulating stress genes are conserved in the plant
like yeasts or humans (Huisinga and Pugh, 2004).
