The nucleotide sequence of SV40 DNA was determined, and the sequence was correlated with known genes of the virus and with the structure of viral messenger RNA's. There is a limited overlap of the coding regions for structural proteins and a complex pattern of leader sequences at the 5' end of late messenger RNA. The sequence of the early region is consistent with recent proposals that the large early polypeptide of SV40 is encoded in noncontinguous segments of DNA.

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Cowhage spicules provide an important model for histamine-independent itch. We determined that the active component of cowhage, termed mucunain, is a novel cysteine protease. We isolated mucunain and demonstrate that both native and recombinant mucunain evoke the same quality of itch in humans. We also show that mucunain is a ligand for protease-activated receptors two and four. These results support and expand the relationship between proteases, protease-activated receptors, and itch.

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Background Substance P (SP) is linked to itch and inflammation through activation of receptors on mast cells and sensory neurons. There is increasing evidence that SP functions through Mas-related G protein–coupled receptors (Mrgprs) in addition to its conventional receptor, neurokinin-1. Objective Because Mrgprs mediate some aspects of inflammation that had been considered mediated by neurokinin-1 receptor (NK-1R), we sought to determine whether itch induced by SP can also be mediated by Mrgprs. Methods Genetic and pharmacologic approaches were used to evaluate the contribution of Mrgprs to SP-induced scratching behavior and activation of cultured dorsal root ganglion neurons from mice. Results SP-induced scratching behavior and activation of cultured dorsal root ganglion neurons was dependent on Mrgprs rather than NK-1R. Conclusion We deduce that SP activates MrgprA1 on sensory neurons rather than NK-1R to induce itch.

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In order to investigate the 5' terminal structural heterogeneity of the 16S size class of SV40 late RNA, we have bound an SV40 DNA fragment labeled at its 5' termini with P32 to the .939-.945 map unit region of late lytic cytoplasmic polyadenylated RNA, used reverse transcriptase to prepare cDNA copies of the 5' termini of this RNA, separated the cDNA products on an 8% polyacrylamide-7 M urea gel and subjected these products to nucleic acid sequence analysis. A number of discrete cDNAs were obtained. Analysis of these cDNAs has suggested the presence of three categories of 16S species all containing the same body extending from residues 1381-2592 (.939-.170 m.u.) but differring in the structure of their leader segments. Members of the first category contain leaders which are colinear with SV40 DNA, have a common 3' terminus at residue 444 and extend varying distances in a 5' direction. The most abundant 16S species contains a leader of 203 nucleotides and is a member of this group. RNAs of the second category contain leaders with an internal gap between residues 211-352. The single RNA comprising the third category contains a leader with a tandem repetition of nucleotides 351-443 at the 3' terminus of its leader.

Sensory neurons expressing Mas-related G protein coupled receptors (Mrgprs) mediate histamine-independent itch. We show that the cysteine protease cathepsin S activates MrgprC11 and evokes receptor-dependent scratching in mice. In contrast to its activation of conventional protease-activated receptors, cathepsin S mediated activation of MrgprC11 did not involve the generation of a tethered ligand. We demonstrate further that different cysteine proteases selectively activate specific mouse and human Mrgpr family members. This expansion of our understanding by which proteases interact with GPCRs redefines the concept of what constitutes a protease-activated receptor. The findings also implicate proteases as ligands to members of this orphan receptor family while providing new insights into how cysteine proteases contribute to itch.