Circular RNAs (circRNAs) encompass a widespread and conserved class of RNAs, which are generated by back-splicing of downstream 5' to upstream 3' splice sites. CircRNAs are tissue-specific and have been implicated in diseases including cancer. They can function as sponges for microRNAs (miRNAs) or RNA binding proteins (RBPs), for example. Moreover, some contain open reading frames (ORFs) and might be translated. The functional relevance of such peptides, however, remains largely elusive. Here, we report that the ORF of circZNF609 is efficiently translated when expressed from a circZNF609 overexpression construct. However, endogenous proteins could not be detected. Moreover, initiation of circZNF609 translation is independent of m6A-generating enzyme METTL3 or RNA sequence elements such as internal ribosome entry sites (IRESs). Surprisingly, a comprehensive mutational analysis revealed that deletion constructs, which are deficient in producing circZNF609, still generate the observed protein products. This suggests that the apparent circZNF609 translation originates from trans-splicing by-products of the overexpression plasmids and underline that circRNA overexpression constructs need to be evaluated carefully, particularly when functional studies are performed.

Chemical modifications are found on almost all RNAs and affect their coding and noncoding functions. The identification of m6A on mRNA and its important role in gene regulation stimulated the field to investigate whether additional modifications are present on mRNAs. Indeed, modifications including m1A, m5C, m7G, 2′-OMe, and Ψ were detected. However, since their abundances are low and tools used for their corroboration are often not well characterized, their physiological relevance remains largely elusive. Antibodies targeting modified nucleotides are often used but have limitations such as low affinity or specificity. Moreover, they are not always well characterized and due to the low abundance of the modification, particularly on mRNAs, generated data sets might resemble noise rather than specific modification patterns. Therefore, it is critical that the affinity and specificity is rigorously tested using complementary approaches. Here, we provide an experimental toolbox that allows for testing antibody performance prior to their use.

Angewandte Chemie International EditionVolume 47, Issue 9 p. 1729-1732 Communication Silacidins: Highly Acidic Phosphopeptides from Diatom Shells Assist in Silica Precipitation In Vitro† Stephan Wenzl Dr., Stephan Wenzl Dr. Lehrstuhl Biochemie I, Universität Regensburg, 93040 Regensburg, Germany, Fax: (+49) 941-943-2936Search for more papers by this authorRobert Hett, Robert Hett Lehrstuhl Biochemie I, Universität Regensburg, 93040 Regensburg, Germany, Fax: (+49) 941-943-2936Search for more papers by this authorPatrick Richthammer, Patrick Richthammer Lehrstuhl Biochemie I, Universität Regensburg, 93040 Regensburg, Germany, Fax: (+49) 941-943-2936Search for more papers by this authorManfred Sumper Prof. Dr., Manfred Sumper Prof. Dr. [email protected] Lehrstuhl Biochemie I, Universität Regensburg, 93040 Regensburg, Germany, Fax: (+49) 941-943-2936Search for more papers by this author Stephan Wenzl Dr., Stephan Wenzl Dr. Lehrstuhl Biochemie I, Universität Regensburg, 93040 Regensburg, Germany, Fax: (+49) 941-943-2936Search for more papers by this authorRobert Hett, Robert Hett Lehrstuhl Biochemie I, Universität Regensburg, 93040 Regensburg, Germany, Fax: (+49) 941-943-2936Search for more papers by this authorPatrick Richthammer, Patrick Richthammer Lehrstuhl Biochemie I, Universität Regensburg, 93040 Regensburg, Germany, Fax: (+49) 941-943-2936Search for more papers by this authorManfred Sumper Prof. Dr., Manfred Sumper Prof. Dr. [email protected] Lehrstuhl Biochemie I, Universität Regensburg, 93040 Regensburg, Germany, Fax: (+49) 941-943-2936Search for more papers by this author First published: 11 February 2008 https://doi.org/10.1002/anie.200704994Citations: 139 † We thank R. Deutzmann and E. Hochmuth for recording the MS spectra and peptide sequencing, and K. Lutz and E. Brunner for recording NMR spectra. The help of R. Merkl in searching the genomic database is gratefully acknowledged. This research was supported by Volkswagenstiftung and the Fonds der Chemischen Industrie. Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Graphical Abstract More decorative than wallpaper: Silica biomineralization in diatoms leads to intricate structures in the cell wall (see SEM image) and depends on structure-directing templates formed by the electrostatically driven assembly of positively charged polyamine derivatives and polyanions. The title peptides are a family of biologically relevant polyanions present in diatom biosilica and composed mainly of serine phosphate and acidic amino acid residues. Citing Literature Supporting Information Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2008/z704994_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article. Volume47, Issue9February 15, 2008Pages 1729-1732 RelatedInformation

A mass of codes: Lysine-rich silaffin proteins from diatoms guide silica formation by self-assembly processes. Aided by mass spectrometry, the analysis of 28 posttranslationally modified lysine residues in silaffin-3 from Thalassiosira pseudonana uncovers an amino acid sequence based code selecting the type of modification. This code may be a key element in the genetic control of species-specific silica architectures. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2007/z702413_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.