Calculations were based on the CT value of each sample during PCR amplification, where –ΔΔCT=−((CTtarget−CTL8)−(CTAvgtarget−CTAvgL8)), and Avg corresponded to the averaged CTs. Results are expressed as relative mRNA steady-state levels of the target gene and normalized to the L8 ribosomal protein. Data were analyzed by one-way ANOVA and for post hoc analysis the Tukey test was used. Statistical significance was considered when p<0.05, and analyses were done with NCSS software. The complete sequence of the LvPCNA cDNA (GenBankJN034913) is 1103 base pairs (bp) long with a 111 bp 5′-untranslated region (5′-UTR) and a 783 bp ORF that includes the initial methionine and the

stop codon. The 3′-UTR contains a canonical polyA+ tail and the polyadenylation signal, both necessary for mRNA stability ( Fig. UMI-77 in vitro 1). The 783 bp Natural Product Library purchase open reading frame (ORF) codes for a protein with 260 amino acid residues

and a theoretical pI of 4.59 and a molecular weight of 28.81 kDa, very similar to PCNA from other decapods such as the shrimp F. chinensis and M. japonicus [19] and [20] and the Chinese mitten crab Eriocheirjaponica sinensis [18] ( Fig. 2). Multiple amino acid sequences alignment with other species showed that the LvPCNA is extremely conserved among invertebrates and vertebrates, and the few residues changes cluster vertebrate and invertebrate PCNA sequences separately. For example, changes from Lys to Arg occur at positions 91 and 248, between invertebrate and vertebrate sequences ( Fig. 2). Nonetheless, the inner-face of the PCNA trimer is mainly positively charged (Lys or Arg residues), and it is represented in color blue ( Fig. 3, panels B and D). The conserved motifs in PCNA (central loop, back-side loop and inter-domain connector loop) were identified in the shrimp PCNA model ( Fig. 3, panel A). These domains are important for the interaction of PCNA with DNA and are

totally conserved. A recent publication of the PCNA from S. cerevisiae reports that mutations of some of the basic residues at this inner-face Terminal deoxynucleotidyl transferase reduce its affinity for DNA and other proteins needed for replication, and consequently impair processivity of DNA replication [37]. All three conserved motifs in PCNA were identified in the shrimp-deduced amino acid sequence. These motifs are important for the interaction of the PCNA/DNA complex within the replisome, like the center loop which interacts with replication factor C (RF-C) and DNA polymerase δ, the inter-domain connecting loop which interacts with DNA polymerase δ and the C-terminal tail which interacts with replication factor C (RF-C) [6], [9] and [41]. It is quite interesting that from yeast to vertebrate and invertebrate animals, PCNA shares the same fold and quaternary structure. This is, that PCNA forms a donut-shaped trimer with each polypeptide made of two functional domains each (Fig. 3, panel A).