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Title: The 73 kD Subunit of the Cleavage and Polyadenylation Specificity Factor (CPSF) Complex Affects Reproductive Development in Arabidopsis

item Dinkins, Randy

Submitted to: Review Article
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/22/2006
Publication Date: 8/3/2006
Citation: Xu, R., Zhao, H., Dinkins, R.D., Cheng, X., Carberrry, G., Li, Q.Q. 2006. The 73 kD Subunit of the Cleavage and Polyadenylation Specificity Factor (CPSF) Complex Affects Reproductive Development in Arabidopsis. Plant Molecular Biology. 61:799-815.

Interpretive Summary: Plant gene expression is dependent on many factors, including promoter strength, presence or absence of enhancer or repressor elements in the DNA, mRNA translation, as well as 3’ mRNA processing and polyadenylation. It is becoming increasingly clear that these components of gene expression are interrelated and some of the proteins required at multiple steps. However, very little is presently known about the mRNA 3´-end processing machinery of higher plants. This work establishes the four major protein components of cleavage and polyadenylation specificity factor (CPSF) in plants based on their similarity to these proteins in mammals. In addition, the results demonstrate that one of these proteins, called CPSF73-I, is required at the proper concentrations within the cells as both overexpression and underexpression of this protein results in developmental abnormalities and lethality. These results demonstrate for the first time the importance of the 3’ mRNA processing in plant growth and development.

Technical Abstract: Cleavage and polyadenylation specificity factor (CPSF) is an important multi-subunit component of the mRNA 3’-end processing apparatus in eukaryotes. We have identified the Arabidopsis CPSF complex that involves five protein subunits named AtCPSF160, AtCPSF100, AtCPSF73-I, AtCPSF73-II and AtCPSF30. There are two CPSF73 like proteins, AtCPSF73-I and AtCPSF73-II, which share homology with the 73 kD subunit of mammalian CPSF complex. AtCPSF73-I appears to correspond to the functionally characterized mammalian CPSF73 and its yeast counterpart while AtCPSF73-II was identified as a novel protein with uncharacterized protein homologues in other multicellular organisms, but not in yeast. Both of the AtCPSF73 proteins are targeted in the nucleus. They are also essential as knockout or knockdown mutants are lethal. In addition, the expression level of AtCPSF73-I is critical for Arabidopsis development as overexpression of AtCPSF73-I is also lethal. Interestingly, transgenic plants carrying an additional copy of the AtCPSF73-I gene, that is, the full-length cDNA under the control of its native promoter, appeared normal but was male sterile due to delayed anther dehiscence. In contrast, we showed previously that a mutation in the AtCPSF73-II gene was detrimental to the genetic transmission of female gametes. Thus, the two 73 kD subunits of AtCPSF complex appear to have specific functions during flower development. The important roles of mRNA 3´-end processing machinery in modulating plant development are discussed.