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To study the expression of four estrogen receptor genes ( erα1, erα2, erβ1, erβ2 ) of female rainbow trout ( Oncorhynchus mykiss ) during first ovarian development, trouts were sampled from different ovarian stages. Serum E 2 (estradiol) was measured by ELISA and estrogen receptors mRNA expression were examined by qRT-PCR. Our results showed a close association between increased erα1 and vitellogenin mRNA expression during ovarian maturation and increased erα2 mRNA expression in mature ovarian stages. Correlation analysis revealed that a negative relationship between serum E 2 and ovarian erβ1 (or hepatic erβ2 ), but ovarian erβ2 mRNA expression was relatively unchanged during first ovarian development. Trout were also reared in different densities as stocking density 1, 2 and 3 (SD1, 4.6–31.1 kg/m 3 ; SD2, 6.6–40.6 kg/m 3 ; SD3, 8.6–49.3 kg/m 3 ) to elucidate effects of high density on estrogen receptor expression. Histology observation showed ovarian development of trout in higher densities were retard with a relatively early stage and fewer vitellogenin accumulation. Trout in high densities showed significantly decreased serum E 2 , erα mRNA expression and increasing trends of erβ mRNA expression. A noticeable increase of ovarian erβ2 mRNA expression was seen in trout when density is approaching to 50 kg/m 3 . In conclusion, we may hypothesize that increased erβ mRNA expression triggered by high density result in decreased erα mRNA expression and vitellogenesis. As a result, ovarian development in higher densities was retard. [ABSTRACT FROM AUTHOR]

Upf1, Upf2, and Upf3 are the principal regulators of nonsense-mediated mRNA decay (NMD), a cytoplasmic surveillance pathway that accelerates the degradation of mRNAs undergoing premature translation termination. These three proteins interact with each other, the ribosome, the translation termination machinery, and multiple mRNA decay factors, but the precise mechanism allowing the selective detection and degradation of nonsense-containing transcripts remains elusive. Here, we have determined the crystal structure of the N-terminal mIF4G domain from Saccharomyces cerevisiae Upf2 and identified a highly conserved region in this domain that is essential for NMD and independent of Upf2's binding sites for Upf1 and Upf3. Mutations within this conserved region not only inactivate NMD but also disrupt Upf2 binding to specific proteins, including Dbp6, a DEAD-box helicase. Although current models indicate that Upf2 functions principally as an activator of Upf1 and a bridge between Upf1 and Upf3, our data suggest that it may also serve as a platform for the association of additional factors that play roles in premature translation termination and NMD. [ABSTRACT FROM AUTHOR]