This helical domain is part of the Xrn1 catalytic core []. Xrn1 is a cytoplasmic 5'-3' exonuclease that degrades decapped mRNAs. This domain can also be found in Xrn2 [].
5'-3'-exoribonucleases are enzymes that degrade RNA by removing terminal nucleotides from the 5' end. 5'-3'exoribonuclease type 1 (Xrn1, also known as kem1) occurs in animal and fungal lineages. In Saccharomyces cerevisiae, Xrn1 can be activated by Dcs1, a non-essential hydrolase that involved in mRNA decapping. The activation of Xrn1 by Dcs1 is important for respiration [].
This domain is found in 5' to 3' exoribonuclease 1 (XRN1) present in Kluyveromyces lactis. XRN1 is involved in transcription, RNA metabolism, and RNA interference. This domain, known as D3, is the third of four domains located far from the active site. These four domains may help to stabilize the N-terminal segment of Xrn1 for catalysis [].
This domain can be found in 5' to 3' exoribonuclease 1 (XRN1) which belong to a family of conserved enzymes in eukaryotes and have important functions in transcription, RNA metabolism, and RNA interference. Xrn1 in fungi and animals is primarily cytosolic and is involved in degradation of decapped mRNAs, nonsense mediated decay, microRNA decay and is essential for proper development. The Xrn1 homologue in Drosophila, known as Pacman, is required for male fertility []. This domain (D1) along with 3 other domains, make up a 510-residue segment following the conserved regions found in XRNs but they are only present in XRN1 and are absent in Rat1/XRN2. The amino acid sequences of these four domains contain an excess of basic residues, suggesting that these domains might help in binding the RNA substrate. Mutational studies carried out in D1 domain show that the mutant forms had dramatically reduced nuclease activity towards ssDNA substrate indicating that domain D1 is required for Xrn1 nuclease activity [].
This domain is found in the 5'-3' exonuclease (XRN1) present in Drosophila melanogaster. XRN1 degrades deadenylated mRNA that has recently been decapped by decapping enzyme 2 (DCP2). DCP2 associates with decapping activators DCP1 and EDC4. The direct interaction between DCP1 and XRN1 couples mRNA decapping to 5' exonucleolytic degradation. This domain is responsible for binding to DCP1. In particular, the helical C-terminal region of the domain contributes to the binding affinity and the specificity of the interaction [].
This domain can be found in 5' to 3' exoribonuclease 1 (XRN1) which belong to a family of conserved enzymes in eukaryotes and have important functions in transcription, RNA metabolism, and RNA interference. Xrn1 in fungi and animals is primarily cytosolic, involved in degradation of decapped mRNAs, nonsense mediated decay, microRNA decay and is essential for proper development. The Xrn1 homologue in Drosophila, known as Pacman, is required for male fertility []. This entry relates to domain 2 and 3 combined which can be found in the 510-residue C-terminal extension found in XRN1 and not in XRN2/Rat1. Domain D2 is formed by two stretches of Xrn1, residues 915-960 and 1134-1151. The presence of domain (D3) is suggested based on structure. This domain is formed by residues 979-1109, in the insert of domain D2. It is suggested that domains D2-D4 may help maintain domain D1 in the correct conformation, thereby indirectly stabilising the conformation of the N-terminal segment [].
This is the C-terminal SH3-like domain which can be found in the exoribonuclease Xrn1. Xrn1 is a 175kDa processive exoribonuclease that is conserved from yeast to mammals which targets cytoplasmic RNA substrates marked by a 5' monophosphate for processive 5'-to-3' degradation. The Sh3-like domain in Xrn1 lacks the canonical SH3 residues normally involved in binding proline-rich peptide motifs and instead engages in non-canonical interactions with the catalytic domain. Additionally it is essential in maintaining the structural integrity of Xrn1, since partial truncation of thisdomain in yeast Xrn1 yields an inactive protein. There is a long loop projecting from the SH3-like domain that contacts the PAZ/Tudor domain, occluding the functional surface that binds RNA or peptide motifs containing methylated arginines, respectively, in canonical PAZ and Tudor domain [].
DIS3-like exonuclease 2 (DIS3L2) is a 3'-5'-exoribonuclease that specifically recognises RNAs polyuridylated at their 3' end and mediates their degradation. It plays an important role in the mRNA degradation pathway alternative to degradation by Xrn1 and the exosome [, ]. This entry also includes DIS3L2 plant homologue, SUPPRESSOR OF VARICOSE (SOV) (At1g77680), which functions in cytoplasmic mRNA decay and suppresses Arabidopsis decapping mutant phenotypes [].
This entry includes 5'-3'exoribonuclease type 1 and type 2. Putative viral exonucleases 059L and 012L, plant Xrn3 and Xrn4 also belong to this family. 5'-3'-exoribonucleases are enzymes that degrade RNA by removing terminal nucleotides from the 5' end. An exosome and a 5'-3'-exoribonuclease are important in the degradation of very unstable transcripts []. 5'-3'exoribonuclease type 1 (Xrn1, also known as kem1) occurs in animal and fungal lineages. In Saccharomyces cerevisiae, Xrn1 can be activated by Dcs1, a non-essential hydrolase that involved in mRNA decapping. The activation of Xrn1 by Dcs1 is important for respiration [].5'-3' exoribonuclease type 2 (Xrn2, also known as Rat1) occurs in animal, plant and fungal lineages. In Saccharomyces cerevisiae, Rat1 serves to terminateRNA polymerase II (RNAPII) molecules engaged in the production of uncapped RNA []. The concomitant loss of Xrn4 and ABH1/CBP80, a subunit of the mRNA cap binding complex, results in Arabidopsis plants manifesting myriad developmental defects [], suggesting that this enzyme is not only important for RNA processing.
