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United States Department of Agriculture

Agricultural Research Service

Title: Changing Transcriptional Initiation Sites and Alternative 5'- and 3'-Splice Site Selection of the First Intron Deploys the Arabidopsis Protein Isoaspartyl Methyltransferase2 Variants to Different Subcellular Compartments)

Author
item Dinkins, Randy
item Majee, Susmita
item Nayak, Nihar
item Martin, David
item Xu, Qilong
item Belcastro, Marisa
item Houtz, Robert
item Beach, Carol
item Downie, A. bruce

Submitted to: Plant Journal
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/6/2008
Publication Date: 5/1/2008
Citation: Dinkins, R.D., Majee, S.M., Nayak, N.R., Martin, D., Xu, Q., Belcastro, M.P., Houtz, R., Beach, C.M., Downie, A. 2008. Changing Transcriptional Initiation Sites and Alternative 5'- and 3'-Splice Site Selection of the First Intron Deploys the Arabidopsis Protein Isoaspartyl Methyltransferase2 Variants to Different Subcellular Compartments. Plant Journal. doi:10.1111/j.1365-313X.2008.03471.x

Interpretive Summary: Arabidopsis thaliana (L.) Heynh. possesses two PROTEIN-L-ISOASPARTATE METHYLTRANSFERASE (PIMT), genes encoding an enzyme capable of repairing, L-isoaspartyl residues, that arise spontaneously in proteins. The PIMT2 produces at least eight transcripts by using four transcriptional initiation sites that contain three different start codons, and 5'- and 3'-alternative splice site selection of the first intron. The transcripts produced proteins capable of converting L-isoaspartate to L-aspartate in small peptide substrates and of rescuing enzymatic activity of damaged GUS in vitro. PIMT:GFP fusion proteins generated detectable signal in the nucleus. However, whether the protein was also detectable in the cytoplasm, endo-membrane system, chloroplasts, and/or mitochondria, depended on the transcript from which it was produced. The implications of using transcriptional mechanisms to expand a single gene's repertoire to protein variants capable of entry into the various subcellular compartments are discussed in light of PIMT’s presumed role repairing damaged proteins.

Technical Abstract: Arabidopsis thaliana (L.) Heynh. possesses two PROTEIN-L-ISOASPARTATE METHYLTRANSFERASE (PIMT), genes encoding an enzyme (EC 2.1.1.77) capable of converting uncoded, L-isoaspartyl residues, arising spontaneously at L-asparaginyl and L-aspartyl sites in proteins, to L-aspartate. PIMT2 produces at least eight transcripts by using four transcriptional initiation sites (TIS; resulting in three different initiating methionines) and both 5'- and 3'-alternative splice site selection of the first intron. The transcripts produced proteins capable of converting L-isoaspartate to L-aspartate in small peptide substrates and of rescuing enzymatic activity of damaged GUS in vitro. PIMT:GFP fusion proteins generated detectable signal in the nucleus. However, whether the protein was also detectable in the cytoplasm, endo-membrane system, chloroplasts, and/or mitochondria, depended on the transcript from which it was produced. The implications of using transcriptional mechanisms to expand a single gene's repertoire to protein variants capable of entry into the cell's various compartments are discussed in light of PIMT’s presumed role repairing the proteome.

Last Modified: 8/24/2016
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