Protein Complex in RNA Processing

published: 12 Jun 2011 (5:17)

Steps of nuclear RNA processing.

Researchers working at Case Western Reserve University School of Medicine successfully identified and described the cellular mechanism, which is critical for maintaining normal cell functions. Dr Eckhard Jankowsky, a Doctorate associate professor and researcher from the school, led the team of researchers. This team examined the functions of a protein complex called as TRAMP in RNA or Ribonucleic acid processing within the cells. The team also identified an important function of the protein called Mtr4p in this process, which initiates degradation of specific RNA. This is a mandatory step in preservation of normal cell functions. The findings of the research have appeared in the journal "Cell" in its June 9, 2011 issue. Dr Jankowsky here is the senior writer.

A range of several different kinds of RNA is required in cellular functions and they need to be properly processed and collected in functional complexes. Dr Jankowsky stated that, any RNA that is defective no longer required or improperly assembled looks similar to the RNA that is used. Therefore, there is a possibility that this defective, no longer required or improperly assembled RNA may interfere in the ongoing processes. The many RNA degradation pathways, which are extremely efficient, are utilized to avoid this and the complex TRAMP initiates one such pathway. This protein complex identifies the RNA positioned for their degradation and tags them by using a number of adenosines. Adenosines are one of the four nucleotides that make RNA. The tags only contain a limited number of adenosines, as RNAs having several adenosines are not recognized any more as degradation targets.

This team of researchers led by Dr Jankowsky included other team members Huijue Jia, who is the School of Medicine's graduate student and Jim Anderson, an associate professor at Marquette University. Jim was the key figure in this discovery of this protein complex TRAMP. He studied this molecular mechanism of how TRAMP marks the RNA. The TRAMP is constituted of the Zn-knuckle protein Air2p, enzyme poly (A) polymerase Trf4p and Mtr4p, which is a RNA helicase. Normally, the Helicase unwinds helices; however, the researchers found that in case of TRAMP, Mtr4p the helicase, controls number of added adenosines. Researchers in their paper have detailed how this number of adenosines appended is controlled by the helicase. The helicase counts the actual number of adenosines, which is normally between 4 and 5, which have been appended with polymerase, and then actively adjusts the polymerase.

Dr Jankowsky explained that, their work has explained a significant step in the RNA degradation and that is, it identifies the cells that mark RNAs ready for degradation in nucleus. He explained that proper tagging is necessary for cell functioning. This research was conducted in Dr Jankowsky's lab at the Center for RNA Molecular Biology in the school. This is just a step for more research in future for examining the steps between RNA tagging and RNA degradation with other enzymes involved in the process.

Huijue Jia, Xuying Wang, Fei Liu, Ulf-Peter Guenther, Sukanya Srinivasan, James T. Anderson, Eckhard Jankowsky. The RNA Helicase Mtr4p Modulates Polyadenylation in the TRAMP Complex. Cell, Volume 145, Issue 6, 890-901

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