mRNA 3' -UTR-mediate translational control through PAS and CPE in sheep oocyte.

In oocytes, the cytoplasmic polyadenylation and maternal mRNAs translation is regulated by cis-elements, including polyadenylation signal (PAS) and cytoplasmic polyadenylation element (CPE) in 3'-UTR. Recent studies illustrate non-canonical polyadenylation mechanisms of translational regulation in mouse oocytes, which is different from that in Xenopus oocytes. However, it is still unclear if this regulation in rodent oocytes functions in the domestic animal oocyte. Here, by using sheep as an animal model, we cloned the 3'-UTRs of Cpeb1 or Btg4 and ligated it into the pRK5-Flag-Gfp vector. Variant numbers and positions of PASs and CPEs within the 3'-UTRs were constructed to detect their effects on translational control. After in vitro-transcription and microinjection into sheep fully grown germinal vesicle stage oocytes, the expression efficiency of mRNAs was detected by the GFP and flag expression. Our results show that: (i) PAS located at the proximal end of 3'-UTR can mediate the translation of the maternal mRNAs, as long as they locate far from CPEs; (ii) The proximal PAS has higher efficiency in regulating transcription than the distal one; (iii) increase of PAS number can promote the translational activity more efficiently; (iv) a single CPE located close to PAS (<50 bp) in 3'-UTRs of Cpeb1 or Btg4 could partially repress translation. In 3'-UTRs of Btg4, two CPEs have a higher inhibitory effect, and three CPEs can completely inhibit mRNA translation. These results confirm the existence of the non-canonical mechanism in domestic animal oocytes.

The effect of catalytic copper pretreatments on CVD graphene growth at different stages.

The controllable synthesis of high-quality and large-area graphene by chemical vapor deposition (CVD) remains a challenge nowadays. The massive grain boundaries in graphene grown on polycrystalline Cu by CVD significantly reduce its carrier mobility, limiting its application in high-performance electronic devices. Here, we confirm that the synergetic pretreatment of Cu with electropolishing and surface oxidation is a more efficient way to further suppress the graphene nucleation density (GND) and to accelerate the growth rate of the graphene domain by CVD. With increasing the growth time, we found that the increasing amount of GND and growth rate of the graphene domain were both decreasing during the whole CVD process when the Cu surface was not oxidized. By contrast, they kept growing over time when the Cu surface was pre-oxidized, which suggested that the change trends of the effects on the GND and growth rate between the Cu surface morphology and oxygen were opposite in the CVD process. In addition, not only the domain shape, but the number of graphene domain layers were impacted as well, and a large number of irregular ellipse graphene wafers with dendritic multilayer emerged when the Cu surface was oxidized.