Pierisins and CARP-1: ADP-Ribosylation of DNA by ARTCs in Butterflies and Shellfish

Abstract

The cabbage butterfly, Pieris rapae, and related species possess a previously unknown ADP-ribosylating toxin, guanine specific ADP-ribosyltransferase. This enzyme toxin, known as pierisin, consists of enzymatic N-terminal domain and receptor-binding C-terminal domain, or typical AB-toxin structure. Pierisin efficiently transfers an ADP-ribosyl moiety to the N(2) position of the guanine base of dsDNA. Receptors for pierisin are suggested to be the neutral glycosphingolipids, globotriaosylceramide (Gb3), and globotetraosylceramide (Gb4). This DNA-modifying toxin exhibits strong cytotoxicity and induces apoptosis in various human cell lines, which can be blocked by Bcl-2. Pierisin also produces detrimental effects on the eggs and larvae of the non-habitual parasitoids. In contrast, a natural parasitoid of the cabbage butterfly, Cotesia glomerata, was resistant to this toxin. The physiological role of pierisin in the butterfly is suggested to be a defense factor against parasitization by wasps. Other type of DNA ADP-ribosyltransferase is present in certain kinds of edible clams. For example, the CARP-1 protein found in Meretrix lamarckii consists of an enzymatic domain without a possible receptor-binding domain. Pierisin and CARP-1 are almost fully non-homologous at the amino acid sequence level, but other ADP-ribosyltransferases homologous to pierisin are present in different biological species such as eubacterium Streptomyces. Possible diverse physiological roles of the DNA ADP-ribosyltransferases are discussed.

Scabin, a Novel DNA-acting ADP-ribosyltransferase from Streptomyces scabies

“…Scabin is clearly a member of the Pierisin subgroup of mART toxins based upon its high sequence identity and common core enzyme pattern with that group. Scabin shares common enzymatic function with the Pierisin subgroup in its ability to target the guanine base within DNA (8). Specifically, Scabin labels nucleosides, mononucleotides, and both dsDNA and ssDNA by transferring ADP-ribose to the exocyclic amino group on the guanine base.…”

“…The members within this subgroup target DNA by attaching ADP-ribose to the exocyclic amino group of the guanine base (4,7,8). We are pursuing further studies with Scabin to determine its role in S. scabies as a putative virulence factor.…”

“…The crystal structure of the apoenzyme has been resolved to 1.4 Å, and we have determined the structure of Scabin with two small molecule inhibitors bound to the active site. It also has sequence similarity to the Pierisin subgroup of mART toxins, as shown by multiple-sequence alignment (4,7,8). Using this information, we identified the Scabin transferase substrate as DNA and other small nucleotides possessing guanine (7).…”

“…In rare cases, mART toxins may target DNA as the macromolecule substrate as in the case of Pierisin-1 (4). Those mART toxins that utilize DNA as a target macromolecule label the guanine base with an ADPribose moiety (7,8).…”

Substrate N2 atom recognition mechanism in pierisin family DNA-targeting, guanine-specific ADP-ribosyltransferase ScARP

“…To date, six pierisins (pierisin-1,-1b, and -2-5), ScARP, and Scabin are considered to belong to the pierisin family (15) and are members of the ARTC subfamily. CARP-1, which is present in certain kinds of edible clams, also ADP-ribosylates calf thymus DNA to produce N 2 -(ADP-ribos-1-yl)-2'-deoxyguanosine (16,17). However, CARP-1 and pierisins share very little sequence homology, suggesting that they are not derived from a common ancestral gene (16).…”