@article{settlage_miller_gruissem_hanley-bowdoin_2001, title={Dual interaction of a geminivirus replication accessory factor with a viral replication protein and a plant cell cycle regulator}, volume={279}, ISSN={["0042-6822"]}, DOI={10.1006/viro.2000.0719}, abstractNote={Geminiviruses replicate their small, single-stranded DNA genomes through double-stranded DNA intermediates in plant nuclei using host replication machinery. Like most dicot-infecting geminiviruses, tomato golden mosaic virus encodes a protein, AL3 or C3, that greatly enhances viral DNA accumulation through an unknown mechanism. Earlier studies showed that AL3 forms oligomers and interacts with the viral replication initiator AL1. Experiments reported here established that AL3 also interacts with a plant homolog of the mammalian tumor suppressor protein, retinoblastoma (pRb). Analysis of truncated AL3 proteins indicated that pRb and AL1 bind to similar regions of AL3, whereas AL3 oligomerization is dependent on a different region of the protein. Analysis of truncated AL1 proteins located the AL3-binding domain between AL1 amino acids 101 and 180 to a region that also includes the AL1 oligomerization domain and the catalytic site for initiation of viral DNA replication. Interestingly, the AL3-binding domain was fully contiguous with the domain that mediates AL1/pRb interactions. The potential significance of AL3/pRb binding and the coincidence of the domains responsible for AL3, AL1, and pRb interactions are discussed.}, number={2}, journal={VIROLOGY}, author={Settlage, SB and Miller, AB and Gruissem, W and Hanley-Bowdoin, L}, year={2001}, month={Jan}, pages={570–576} }
 @article{kong_orozco_roe_nagar_ou_feiler_durfee_miller_gruissem_robertson_et al._2000, title={A geminivirus replication protein interacts with the retinoblastoma protein through a novel domain to determine symptoms and tissue specificity of infection in plants}, volume={19}, ISSN={["0261-4189"]}, DOI={10.1093/emboj/19.13.3485}, abstractNote={Geminiviruses replicate in nuclei of mature plant cells after inducing the accumulation of host DNA replication machinery. Earlier studies showed that the viral replication factor, AL1, is sufficient for host induction and interacts with the cell cycle regulator, retinoblastoma (pRb). Unlike other DNA virus proteins, AL1 does not contain the pRb binding consensus, LXCXE, and interacts with plant pRb homo logues (pRBR) through a novel amino acid sequence. We mapped the pRBR binding domain of AL1 between amino acids 101 and 180 and identified two mutants that are differentially impacted for AL1–pRBR interactions. Plants infected with the E‐N140 mutant, which is wild‐type for pRBR binding, developed wild‐type symptoms and accumulated viral DNA and AL1 protein in epidermal, mesophyll and vascular cells of mature leaves. Plants inoculated with the KEE146 mutant, which retains 16% pRBR binding activity, only developed chlorosis along the veins, and viral DNA, AL1 protein and the host DNA synthesis factor, proliferating cell nuclear antigen, were localized to vascular tissue. These results established the importance of AL1–pRBR interactions during geminivirus infection of plants.}, number={13}, journal={EMBO JOURNAL}, author={Kong, LJ and Orozco, BM and Roe, JL and Nagar, S and Ou, S and Feiler, HS and Durfee, T and Miller, AB and Gruissem, W and Robertson, D and et al.}, year={2000}, month={Jul}, pages={3485–3495} }
 @article{orozco_miller_settlage_hanley-bowdoin_1997, title={Functional domains of a geminivirus replication protein}, volume={272}, DOI={10.1074/jbc.272.15.9840}, abstractNote={Tomato golden mosaic virus, a member of the geminivirus family, has a single-stranded DNA genome that is replicated and transcribed in infected plant cells through the concerted action of viral and host factors. One viral protein, AL1, contributes to both processes by binding to a directly repeated, double-stranded DNA sequence located in the overlapping (+) strand origin of replication and AL1 promoter. The AL1 protein, which occurs as a multimeric complex in solution, also catalyzes DNA cleavage during initiation of rolling circle replication. To identify the tomato golden mosaic virus AL1 domains that mediate protein oligomerization, DNA binding, and DNA cleavage, a series of truncated AL1 proteins were produced in a baculovirus expression system and assayed for each activity. These experiments localized the AL1 oligomerization domain between amino acids 121 and 181, the DNA binding domain between amino acids 1 and 181, and the DNA cleavage domain between amino acids 1 and 120. Deletion of the first 29 amino acids of AL1 abolished DNA binding and DNA cleavage, demonstrating that an intact N terminus is required for both activities. The observation that the DNA binding domain includes the oligomerization domain suggested that AL1-AL1 protein interaction may be a prerequisite for DNA binding but not for DNA cleavage. The significance of these results for AL1 function during geminivirus replication and transcription is discussed.}, number={15}, journal={Journal of Biological Chemistry}, author={Orozco, B. M. and Miller, A. B. and Settlage, S. B. and Hanley-Bowdoin, Linda}, year={1997}, pages={9840–9846} }
 @article{ach_durfee_miller_taranto_hanleybowdoin_zambryski_gruissem_1997, title={RRB1 and RRB2 encode maize retinoblastoma-related proteins that interact with a plant D-type cyclin and geminivirus replication protein}, volume={17}, ISSN={["0270-7306"]}, DOI={10.1128/MCB.17.9.5077}, abstractNote={Unlike mammalian and yeast cells, little is known about how plants regulate G1 progression and entry into the S phase of the cell cycle. In mammalian cells, a key regulator of this process is the retinoblastoma tumor suppressor protein (RB). In contrast, G1 control in Saccharomyces cerevisiae does not utilize an RB-like protein. We report here the cloning of cDNAs from two Zea mays genes, RRB1 and RRB2, that encode RB-related proteins. Further, RRB2 transcripts are alternatively spliced to yield two proteins with different C termini. At least one RRB gene is expressed in all the tissues examined, with the highest levels seen in the shoot apex. RRB1 is a 96-kDa nuclear protein that can physically interact with two mammalian DNA tumor virus oncoproteins, simian virus 40 large-T antigen and adenovirus E1A, and with a plant D-type cyclin. These associations are abolished by mutation of a conserved cysteine residue in RRB1 that is also essential for RB function. RRB1 binding potential is also sensitive to deletions in the conserved A and B domains, although differences exist in these effects compared to those of human RB. RRB1 can also bind to the AL1 protein from tomato golden mosaic virus (TGMV), a protein which is essential for TGMV DNA replication. These results suggest that G1 regulation in plant cells is controlled by a mechanism which is much more similar to that found in mammalian cells than that in yeast.}, number={9}, journal={MOLECULAR AND CELLULAR BIOLOGY}, author={Ach, RA and Durfee, T and Miller, AB and Taranto, P and HanleyBowdoin, L and Zambryski, PC and Gruissem, W}, year={1997}, month={Sep}, pages={5077–5086} }