Evidence providing new insights into TOB-promoted deadenylation and supporting a link between TOB's deadenylation-enhancing and antiproliferative activities
Authors: Ann-Bin Shyu
Chyi-Ying A Chen
Nader Ezzeddine
Journal: Molecular and Cellular Biology (2012)
Discipline: MOLECULAR BIOLOGY & GENETICS
Keywords: TOB1; TOB2; cell proliferation; mRNA deadenylation; CAF1-CCR4 deadenylase complex
Affiliations: Department of Biochemistry and Molecular Biology, The University of Texas Medical School, Houston, Texas, USA.

Abstract:  The mammalian TOB1 and TOB2 proteins have emerged as key players in repressing cell proliferation. Accumulating evidence indicates that TOBs regulate mRNA deadenylation. A recruitment model was proposed in which TOBs promote deadenylation by recruiting CAF1-CCR4 deadenylase complex to the 3' end of mRNAs by simultaneously binding CAF1 and PABP. However, the exact molecular mechanism underlying TOB-promoted deadenylation remains unclear. It is also unclear whether TOBs' antiproliferative and deadenylation-promoting activities are connected. Here, we combine biochemical analyses with a functional assay directly monitoring deadenylation and mRNA decay to characterize the effects of tethering TOBs or their mutant derivatives to mRNAs. The results provide direct evidence supporting the recruitment model and reveal a link between TOBs' antiproliferative and deadenylation-promoting activities. We also find that TOBs' actions in deadenylation are independent of the phosphorylation state of three serines known to regulate antiproliferative actions, suggesting that TOBs arrest cell growth through at least two different mechanisms. TOB1 and TOB2 were interchangeable in the properties tested here, indicating considerable functional redundancy between the two proteins. We propose that their multiple modes of modulating mRNA turnover and arresting cell growth permit the TOB proteins to coordinate their diverse roles in controlling cell growth and differentiation. 

Retracted: No

PubPeer comments:
 2017 correction. http: mcb.asm.org content 37 14 e00208-17.short , 
 This paper was part of a structured search for image problems in papers published in Molecular and Cellular Biology, published here: https: mcb.asm.org content 38 20 e00309-18.long Here are the problems found during this search. Figure 3A: * Blue boxes: The three A- lanes in the top panels all looked similar to each other. * Red boxes: Two A- lanes in the bottom panels looked similar to each other. ![file] This issue, where the same lane was admittedly cut and pasted to represent lanes in different blots and experiments, was addressed with a correction. The correction (see link above in comment #1) reads:  *The Au2212 lanes in both the top and bottom panels were duplicated. The corrected images, obtained from original data, should appear as shown below. These changes do not affect the interpretation of the data and conclusions of the study.* I am not sure if this admitted photographic alteration should be addressed with a correction. , 
 There was an additional problem in this paper, found in Figure 5 and also reported to the journal in 2016. This problem was not addressed in the correction. Figure 5. * Green arrows: The first two lanes of the a-tubulin panel in Figure 5A look similar to two lanes in one of the a-tubulin panels in Figure 5B. ![file] , 
 #2 What happened was that when conducting the experiments for Fig. 3A, my postdoc ran three sets (MS2, MS2-TOB1 and MS2-TOB2 under CAF1 siRNA treatment) or two sets (MS2 and MS2-TOB1 under control siRNA treatment) of RNA samples on the same RNA gel with one poly(A) minus RNA lane (A-) served as a reference size marker. Later on for our publication presentation, he thought it s OK to cut and pasted each of the original set as a single group and then copied and pasted the A- size marker lane to the other groups to help to see where the poly(A) minus BBB RNA migrates, because these groups of RNA samples were originally run on the same gel sharing the same A- size marker. In retrospect, what we should have done was to present the original images without separating them into individual groups and draw a dotted line across all lanes to indicate A- position to avoid this concern. As you can see, the correction does not compromise our interpretation of the results shown in Fig. 3A at all, which was also agreed by the editor who handled the allegation. My apologies for not catching this presentation artwork error before our manuscript was published and any inconvenience or concern this may have caused. , 
 #3 Thank you for bringing your concern about Fig. 5A and B in our 2012 MCB paper to my attention. The reason why this particular concern was not addressed in our 2017 correction to MCB was because the editor said in his email that their analysis did not confirm the allegations concerning Figure 5A and B. However, after receiving the concern you raised from PubPeer on March 9, 2021, I decided to go back to our previous data and various versions of the figures for our 2012 MCB paper. I realized that when we assembled the final panels for Fig. 5 for submission, we took an incorrect version of the panel for Fig. 5A. (By the way, the alpha-tubulin control for Fig. 5B is correct.) As you pointed out, the tubulin loading control in this particular panel of Fig. 5A has a problem. It was likely due to some confusions related to probing various tubulin western membrane strips from several experiments all together. Later on we did get this straightened. The correct panel for Fig. 5A that should have been used in our 2012 MCB publication is shown below: ![file] As you can see, this correction dose not compromise our interpretation of the results for Fig. 5A at all, i.e., GFP-12bs expression is only diminished by tethering the ectopically expressed MS2-TOB1 or MS2-TOB2 protein (see middle panel, the second and third lanes from left) in our 2012 MCB paper. Again, my apologies for the error and any inconvenience or concern it may have caused. ,