Subsystem: At1g26220 At1g32070

This subsystem's description is:

Hypothesis: At1g32070 was shown to interacts with the geminivirus movement protein NSP and to acetylates viral coat protein (CP) in vitro, but not NSP. Analysis of protein-proten interaction in Synechocystis 6803 identified strong interaction of At1g32070 homolog with Tyrosine recombinase XerC (slr0733), suggestion that the "original" function of At1g32070 orthologs in plant cell (hijacked by geminivirus) is associated with replication of chloroplast chromosome (via acetylation??). Co-expression of AtNSI with At1g65260 (PLASTID TRANSCRIPTIONALLY ACTIVE protein PTAC4) indirectly supports this hypothesis

1. The Arabidopsis 2-member gene family At1g26220//At1g32070 includes:

- At1g32070: acetyltransferase AtNSI, that was shown to interacts with the geminivirus movement protein NSP (McGarry et al., 2003). It was shown "to acetylate histones, but not NSP, in vitro. Rather, AtNSI specifically acetylates the viral coat protein. AtNSI is a nuclear protein but does NOT act as a transcriptional coactivator in vitro, which distinguishes it from known eukaryotic histone acetyltransferases..." (McGarry et al., 2003).

- At1g26220: yet uncharacterized putative N-acetyltransferase (GNAT) family

2. Both proteins are predicted to be targeted to chloroplast stroma (by TargetP); At1g32070 was also detected in the nucleus (McGarry et al., 2003).

3. The At1g32070 (AtNSI) and At1g26220 homologs are present in nearly all sequence cyanobacterial genomes. Notably both proteins are located in the vicinity of each other in the genomes of Anabaena sp. and Nostoc sp.

4. Despite it's proven function as histone acetyltransferase (McGarry et al., 2003), AtNSI is much more similar on a sequence level to putative cyanobacterial acetyltransferases [encoded in this Subsystem], than to "classic" histone acetyltransferases. Furthermore, At1g26220//At1g32070 are not present in any ekaryotes other than plants and algae

5. Protein-protein interaction study in Synechocystis 6803 (Sato et al., 2007) identified a strong interaction of Tyrosine recombinase XerC (slr0733), [encoded by chromosome as well as by several cyano plasmids] with AtNSI homolog (sll0286), as well as with hypothetical protein sll0284 (containing a HAS barrel docking domain and a DUF87 domain). Homologs of both cyanobacterial interaction partners are not detectable in AT genome, however this finding might suggest that the "original" function of At1g32070 orthologs in plant cell (hijacked by geminivirus) is associated with replication of chloroplast chromosome. Co-expression of AtNSI with At1g65260 (PLASTID TRANSCRIPTIONALLY ACTIVE protein PTAC4) indirectly supports this hypothesis

6. Alternative hypothesis: Co-localization of At1g26220//At1g32070 with SecFD in Nostoc and Anabaena, and with SecA in Prochlorococci might indicate involvement in regulation of protein transport (via acetylation?)

For more information, please check out the description and the additional notes tabs, below

DiagramFunctional RolesSubsystem SpreadsheetDescriptionAdditional Notes 

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Group Alias
Abbrev.Functional RoleReactionsScenario ReactionsGOLiterature
SubsetsColoring
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expanded


  
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Taxonomy Pattern 
Organism 
Domain
Variant [?] 
active
sll0284At1g26220At1g32070slr1916XerCXerDSecASecFSecD
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Hypothesis: At1g32070 was shown to interacts with the geminivirus movement protein NSP and to acetylates viral coat protein (CP) in vitro, but not NSP. Analysis of protein-proten interaction in Synechocystis 6803 identified strong interaction of At1g32070 homolog with Tyrosine recombinase XerC (slr0733), suggestion that the "original" function of At1g32070 orthologs in plant cell (hijacked by geminivirus) is associated with replication of chloroplast chromosome (via acetylation??). Co-expression of AtNSI with At1g65260 (PLASTID TRANSCRIPTIONALLY ACTIVE protein PTAC4) indirectly supports this hypothesis

1. The Arabidopsis 2-member gene family At1g26220//At1g32070 includes:

- At1g32070: acetyltransferase AtNSI, that was shown to interacts with the geminivirus movement protein NSP (McGarry et al., 2003). It was shown "to acetylate histones, but not NSP, in vitro. Rather, AtNSI specifically acetylates the viral coat protein. AtNSI is a nuclear protein but does NOT act as a transcriptional coactivator in vitro, which distinguishes it from known eukaryotic histone acetyltransferases..." (McGarry et al., 2003).

- At1g26220: yet uncharacterized putative N-acetyltransferase (GNAT) family

2. Both proteins are predicted to be targeted to chloroplast stroma (by TargetP); At1g32070 was also detected in the nucleus (McGarry et al., 2003).

3. The At1g32070 (AtNSI) and At1g26220 homologs are present in nearly all sequence cyanobacterial genomes. Notably both proteins are located in the vicinity of each other in the genomes of Anabaena sp. and Nostoc sp.

4. Despite it's proven function as histone acetyltransferase (McGarry et al., 2003), AtNSI is much more similar on a sequence level to putative cyanobacterial acetyltransferases [encoded in this Subsystem], than to "classic" histone acetyltransferases. Furthermore, At1g26220//At1g32070 are not present in any ekaryotes other than plants and algae

5. Protein-protein interaction study in Synechocystis 6803 (Sato et al., 2007) identified a strong interaction of Tyrosine recombinase XerC (slr0733), [encoded by chromosome as well as by several cyano plasmids] with AtNSI homolog (sll0286), as well as with hypothetical protein sll0284 (containing a HAS barrel docking domain and a DUF87 domain). Homologs of both cyanobacterial interaction partners are not detectable in AT genome, however this finding might suggest that the "original" function of At1g32070 orthologs in plant cell (hijacked by geminivirus) is associated with replication of chloroplast chromosome. Co-expression of AtNSI with At1g65260 (PLASTID TRANSCRIPTIONALLY ACTIVE protein PTAC4) indirectly supports this hypothesis

6. Alternative hypothesis: Co-localization of At1g26220//At1g32070 with SecFD in Nostoc and Anabaena, and with SecA in Prochlorococci might indicate involvement in regulation of protein transport (via acetylation?)
References

1. McGarry RC, Barron YD, Carvalho MF, Hill JE, Gold D, Cheung E, Kraus WL, Lazarowitz SG. 2003. A novel Arabidopsis acetyltransferase interacts with the geminivirus movement protein NSP. - Plant Cell, 15(7):1605-18.

2. A large-scale protein protein interaction analysis in Synechocystis sp. PCC6803.
Sato S, Shimoda Y, Muraki A, Kohara M, Nakamura Y, Tabata S. DNA Res. 2007 Oct 31;14(5):207-16.