@article{orozco_kong_batts_elledge_hanley-bowdoin_2000, title={The multifunctional character of a geminivirus replication protein is reflected by its complex oligomerization properties}, volume={275}, ISSN={["0021-9258"]}, DOI={10.1074/jbc.275.9.6114}, abstractNote={Tomato golden mosaic virus (TGMV), a member of the geminivirus family, encodes one essential replication protein, AL1, and recruits the rest of the DNA replication apparatus from its plant host. TGMV AL1 is an oligomeric protein that binds double-stranded DNA and catalyzes cleavage and ligation of single-stranded DNA. The oligomerization domain, which is required for DNA binding, maps to a region that displays strong sequence and structural homology to other geminivirus Rep proteins. To assess the importance of conserved residues, we generated a series of site-directed mutations and analyzed their impact on AL1 function in vitro and in vivo. Two-hybrid experiments revealed that mutation of amino acids 157–159 inhibited AL1-AL1 interactions, whereas mutations at nearby residues reduced complex stability. Changes at positions 157–159 also disrupted interaction between the full-length mutant protein and a glutathione S-transferase-AL1 oligomerization domain fusion in insect cells. The mutations had no detectable effect on oligomerization when both proteins contained full-length AL1 sequences, indicating that AL1 complexes can be stabilized by amino acids outside of the oligomerization domain. Nearly all of the oligomerization domain mutants were inhibited or severely attenuated in their ability to support AL1-directed viral DNA replication. In contrast, the same mutants were enhanced for AL1-mediated transcriptional repression. The replication-defective AL1 mutants also interfered with replication of a TGMV A DNA encoding wild type AL1. Full-length mutant AL1 was more effective in the interference assays than truncated proteins containing the oligomerization domain. Together, these results suggested that different AL1 complexes mediate viral replication and transcriptional regulation and that replication interference involves multiple domains of the AL1 protein.}, number={9}, journal={JOURNAL OF BIOLOGICAL CHEMISTRY}, author={Orozco, BM and Kong, LJ and Batts, LA and Elledge, S and Hanley-Bowdoin, L}, year={2000}, month={Mar}, pages={6114–6122} }
 @article{gladfelter_eagle_fontes_batts_hanley-bowdoin_1997, title={Two domains of the AL1 protein mediate geminivirus origin recognition}, volume={239}, ISSN={["0042-6822"]}, DOI={10.1006/viro.1997.8869}, abstractNote={The geminiviruses tomato golden mosaic virus (TGMV) and bean golden mosaic virus (BGMV) have bipartite genomes. Their A and B DNA components contain cis-acting sequences that function as origins of replication, while their A components encode the trans-acting replication proteins--AL1 and AL3. Earlier experiments demonstrated that virus-specific interactions between the cis- and trans-acting functions are required for TGMV and BGMV replication and that the AL1 proteins of the two viruses specifically bind their respective origins. In the current study, characterization of AL1 and AL3 proteins produced from plant expression cassettes in transient replication assays revealed that interaction between AL1 and the origin is responsible for virus-specific replication. The AL3 protein does not contribute to specificity but can be preferred by its cognate AL1 protein when replication is impaired. Analysis of chimeric proteins showed that two regions of AL1 act as specificity determinants during replication. The first domain is located between amino acids 1 and 116 and recognizes the AL1 origin binding site. The second region, which is between amino acids 121 and 209, is not dependent on the known AL1 DNA binding site. Analysis of wild type and chimeric proteins in transient transcription assays showed that AL1 also represses its own promoter in a virus-specific manner. Transcriptional specificity is conferred primarily by AL1 amino acids 1-93 with amino acids 121-209 making a smaller contribution. Together, these results demonstrated that the virus-specific interactions of AL1 during replication and transcription are complex, involving at least two discreet domains of the protein.}, number={1}, journal={VIROLOGY}, author={Gladfelter, HJ and Eagle, PA and Fontes, EPB and Batts, L and Hanley-Bowdoin, L}, year={1997}, month={Dec}, pages={186–197} }