Distribution of Human Sapovirus Strain Genotypes over the Last Four Decades in Japan: a Global Perspective.

Sapovirus (SaV) infections are a public health problem because they cause acute gastroenteritis in humans of all ages, both sporadically and as outbreaks. However, only a limited amount of SaV sequence information, especially whole-genome sequences for all the SaV genotypes, is publicly available. Therefore, in this study, we determined the full/near-full-length genomic sequences of 138 SaVs from the 2001 to 2015 seasons in 13 prefectures across Japan. The genogroup GI was predominant (67%, n = 92), followed by genogroups GII (18%, n = 25), GIV (9%, n = 12), and GV (6%, n = 9). Within the GI genogroup, four different genotypes were identified: GI.1 (n = 44), GI.2 (n = 40), GI.3 (n = 7), and GI.5 (n = 1). We then compared these Japanese SaV sequences with 3,119 publicly available human SaV sequences collected from 49 countries over the last 46 years. The results indicated that GI.1, and GI.2 have been the predominant genotypes in Japan, as well as in other countries, over at least four decades. The 138 newly determined Japanese SaV sequences together with the currently available SaV sequences, could facilitate a better understanding of the evolutionary patterns of SaV genotypes.

Nucleocytoplasmic shuttling of IPAS by its unique nuclear import and export signals unshared with other HIF-3α splice variants.

Inhibitory Per/Arnt/Sim (PAS) domain protein (IPAS) is a splice variant of hypoxia-inducible factor (HIF)-3α, and possesses two entirely different functions. One is as a transcriptional repressor against HIF-dependent hypoxic gene activation. The other is as a pro-apoptotic factor by direct binding to the pro-survival protein Bcl-xL and its related proteins on mitochondria. Presently, the regulatory mechanism that determines the intracellular distribution of IPAS to fulfill each of the two functions is unknown. As a first step towards elucidation of the mechanism, nucleocytoplasmic transport signals of IPAS were explored. A bipartite-like nuclear localization signal (NLS) was found in the N-terminal region by the deletion and mutation analysis of EGFP-IPAS. In addition, the helix-loop-helix domain showed weak nuclear import/retention activity. A leptomycin B-sensitive nuclear export signal (NES) was localized in the C-terminal region of the protein. A proline-rich region supported the NES activity. These NLS and NES are not carried by the other variants of HIF-3α due to differential exon usage. These results strongly suggest that IPAS is a nucleocytoplasmic shuttling protein.