TY - JOUR
T1 - Changing transcriptional initiation sites and alternative 5′- and 3′-splice site selection of the first intron deploys Arabidopsis PROTEIN ISOASPARTYL METHYLTRANSFERASE2 variants to different subcellular compartments
AU - Dinkins, Randy D.
AU - Majee, Susmita Maitra
AU - Nayak, Nihar R.
AU - Martin, David
AU - Xu, Qilong
AU - Belcastro, Marisa P.
AU - Houtz, Robert L.
AU - Beach, Carol M.
AU - Downie, A. Bruce
PY - 2008/7
Y1 - 2008/7
N2 - Arabidopsis thaliana (L.) Heynh. possesses two PROTEIN-L-ISOASPARTATE METHYLTRANSFERASE (PIMT) genes encoding enzymes (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 produce mature proteins capable of converting l-isoaspartate to l-aspartate in small peptide substrates. PIMT:GFP fusion proteins generated a 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. On-blot-methylation of proteins, prior to the completion of germination, indicated that cruciferin subunits contain isoaspartate. 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 in repairing the proteome.
AB - Arabidopsis thaliana (L.) Heynh. possesses two PROTEIN-L-ISOASPARTATE METHYLTRANSFERASE (PIMT) genes encoding enzymes (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 produce mature proteins capable of converting l-isoaspartate to l-aspartate in small peptide substrates. PIMT:GFP fusion proteins generated a 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. On-blot-methylation of proteins, prior to the completion of germination, indicated that cruciferin subunits contain isoaspartate. 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 in repairing the proteome.
KW - Isoaspartate
KW - Methyltransferase
KW - Repair
KW - Splicing
KW - Subcellular compartment
KW - Transcription
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U2 - 10.1111/j.1365-313X.2008.03471.x
DO - 10.1111/j.1365-313X.2008.03471.x
M3 - Article
C2 - 18318686
AN - SCOPUS:47249116661
SN - 0960-7412
VL - 55
SP - 1
EP - 13
JO - Plant Journal
JF - Plant Journal
IS - 1
ER -