Editors' ChoiceTranscription

Endogenous Antisense

STKE  19 Jun 2001:
Vol. 2001, Issue 87, pp. tw9
DOI: 10.1126/stke.2001.87.tw9

A search for genes in Lotus japonicus related to a nodule-specific transcript LjNOD16 led to the identification of a gene family encoding proteins with an NH2-domain homologous to the yeast phosphatidylinositol transfer protein (PITP). The predicted proteins also have the conserved COOH-domain with two α helices and a positively charged COOH-terminus found in Nlj16 (the protein encoded by LjNOD16), which is involved in membrane targeting. The gene from which Nlj16 is derived (LjPLP-IV) had an unusual expression pattern, detected by Northern analysis, with sense transcripts expressed in flowers and antisense transcripts expressed in nodules. Analysis of the gene showed a bidirectional promoter in intron 10 that was able to direct expression of a reporter gene oriented in either the sense or antisense direction in nodule tissue. Analysis of the ability of the full-length sense-directed transcript of LjPLP-IV to rescue yeast deficient in PITP suggested that the COOH-terminal Nlj16 domain inhibited PITP activity of LjPLP-IV. The PITP activity of the NH2 domain of LjPLP-IV was confirmed by assaying directly the transferase activity for phosphatidylinositol and phosphatidylcholine in recombinant protein expressed in Escherichia coli. The authors propose that the bidirectional promoter producing antisense provides a mechanism for controlling expression of the LjPLP-IV and the autoinhibitory COOH-terminus provides yet another posttranslational mechanism for regulating PITP activity. This regulation of PITP is most likely important, because PITP activity can control the levels of phosphatidylinositol available for enzymes involved in producing second messenger signaling molecules from this lipid.

P. Kapranov, S. M. Routt, V. A Bankaitis, F. J. de Bruijn, K. Szczyglowski, Nodule-specific regulation of phosphatidylinositol transfer protein expression in Lotus japonicus. Plant Cell 13, 1369-1382 (2001). [Abstract] [Full Text]