{'fraction_non_alphanumeric': 0.03237095363079615, 'fraction_numerical': 0.011373578302712161, 'mean_word_length': 5.809523809523809, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Biochemical Characterization of Yeast Xrn1.

Messenger RNA degradation is an important component of overall gene expression. During the final step of eukaryotic mRNA degradation, exoribonuclease 1 (Xrn1) carries out 5'→3' processive, hydrolytic degradation of RNA molecules using divalent metal ion catalysis. To initiate studies of the 5'→3' RNA decay machinery in our lab, we expressed a C-terminally truncated version of Saccharomyces cerevisiae Xrn1 and explored its enzymology using a second-generation, time-resolved fluorescence RNA degradation assay (TRFRD). Using this system, we quantitatively explore Xrn1's preference for 5'-monophosphorylated RNA substrates, pH dependence, and the importance of active site mutations in the molecule's conserved catalytic core. Furthermore, we explore Xrn1's preference for RNAs containing a 5' single-stranded region in both an intermolecular hairpin structure and in an RNA/DNA hybrid duplex system. These results both expand and solidify our understanding of Xrn1, a centrally important enzyme whose biochemical properties have implications in numerous RNA degradation and processing pathways.