Stabilization of SMAR1 mRNA by PGA2 involves a stem–loop structure in the 5′ UTR
Authors: Shravanti Rampalli
Samit Chattopadhyay
Richard G Pestell
Kadreppa Sreenath
Lakshminarasimhan Pavithra
Surajit Sinha
Journal: Nucleic Acids Research (2007)
Discipline: BIOLOGY & BIOCHEMISTRY
Keywords: Prostaglandins; SMAR1; mRNA stability; PGA2; nucleoprotein complex
Affiliations: National Centre for Cell Science, Ganeshkhind, Pune 411007, Maharashtra, India.

Abstract:  Prostaglandins are anticancer agents known to inhibit tumor cell proliferation both in vitro and in vivo by affecting the mRNA stability. Here we report that a MAR-binding protein SMAR1 is a target of Prostaglandin A2 (PGA2) induced growth arrest. We identify a regulatory mechanism leading to stabilization of SMAR1 transcript. Our results show that a minor stem and loop structure present in the 5' UTR of SMAR1 (1-UTR) is critical for nucleoprotein complex formation that leads to SMAR1 stabilization in response to PGA2. This results in an increased SMAR1 transcript and altered protein levels, that in turn causes downregulation of Cyclin D1 gene, essential for G1/S phase transition. We also provide evidence for the presence of a variant 5' UTR SMAR1 (17-UTR) in breast cancer-derived cell lines. This form lacks the minor stem and loop structure required for mRNA stabilization in response to PGA2. As a consequence of this, there is a low level of endogenous tumor suppressor protein SMAR1 in breast cancer-derived cell lines. Our studies provide a mechanistic insight into the regulation of tumor suppressor protein SMAR1 by a cancer therapeutic PGA2, that leads to repression of Cyclin D1 gene. 

Retracted: No

PubPeer comments:
 Can author clarify following issue: ![file] , 
 14 March 2022 correction. https: academic.oup.com nar advance-article doi 10.1093 nar gkac168 6548302 The authors regret the presence of undisclosed image splicing in Figure 5, panels D and E of their article. The authors also wish to report four image assembly errors in Figure 5, panels D and E as detailed below. The errors have most likely arisen while working with multiple files with different exposures. While the authors do not have access to the original raw data which was generated over 17 years ago, the same experimental data in its earliest form, was included in the thesis of one of the authors, Dr. Shravanti Rampalli u2018Regulation of Retroviral and Eukaryotic Transcription through MAR sequences and MAR binding protein SMAR1u2019 submitted to the University of Pune, India in June 2005. This information is used here to update Figures 5D and 5E. Error 1: - Figure 5D, lanes 5u20137 and Figure 5E, lanes 13u201315 are duplicate images. Figure 5D, lanes 5u20137 is incorrect. The correct image is shown in the thesis in panel B, PGA2, SMAR1. - Figure 5D, lanes 11u201313 and Figure 5E, lanes 1u20133 are duplicate images. Figure 5D, lanes 11u201313 is incorrect. The correct image is shown in the thesis in panel B, PGA2, HDAC1. Error 2: Figure 5D, lanes 6u20137 and lanes 12u201313, the labels for the test siRNA and scrambled siRNA were swapped during image assembly. Error 3: Figure 5D, lanes 15u201316, the labels were swapped during figure assembly. Error 4: Figure 5E, lanes 16u201318 and Figure 5D, lanes 14u201317 are duplicate images. Figure 5E, lanes 16u201318 is incorrect. Experiments involving data for Figure 5E lanes 16u201318 were completed after the thesis was submitted. The uncropped gel image is provided below. The correct gel image corresponding to Probe III (Figure 5E lanes 16u201318) has been included in the corrected Figure 5E below. Since this is a different experiment, the signal intensity varies from the previously published subpanel. Original data as presented in the thesis (showing the panels used for assembly): ChIP samples highlighted in blue box are from the thesis and correspond to Figure 5D lanes 5u20137 and 11- 13, which should have been included in the article figure. The thesis panel A and panel D (subpanel 3) are correctly included in the article Figure 5D as lanes 1u20134 (SMAR1 ChIP after PGA2 treatment) and lanes 8u201310, respectively (HDAC1 ChIP after PGA2 treatment). In all panels, the lower strong bands which correspond to primer dimers were not included during image assembly. This was done as a standard procedure to improve comprehension. The article does not include subpanel (293) from Panel A. Corrected Figure 5D. The correct panels for the siRNA experiments have now been provided in the corrected Figure 5D. Since these are separate experiments the signal intensities differ. Figure 5E, lanes 16u201318, original data: The ChIP data indicated in the blue box corresponds to Figure 5E, lanes 16u201318, which should have been included in the article figure. Panel C, and panel D, subpanels 1 and 2 were used correctly to assemble the rest of Figure 5E. Corrected Figure 5D-E: This new figure 5D contains the replaced panels for SMAR1 and HDAC1 ChIP upon SMAR1 and scrambled siRNA after PGA2 treatment. The new figure 5E contains the replaced ChIP image for SMAR1 occupancy on probe III for both treatment conditions. The interpretation of the data and the conclusions of the article are unaffected. However, the authors sincerely apologise to the readers and publisher for the inaccuracies. ,