The ribosome stalk is essential for recruitment of translation factors. In yeast, P0 and Rpl12 correspond to bacterial L10 and L11 and form the stalk base of mature ribosomes, whereas Mrt4 is a nuclear paralogue of P0. In this study, we show that the dual-specificity phosphatase Yvh1 is required for the release of Mrt4 from the pre-60S subunits. Deletion of YVH1 leads to the persistence of Mrt4 on pre-60S subunits in the cytoplasm. A mutation in Mrt4 at the protein–RNA interface bypasses the requirement for Yvh1. Pre-60S subunits associated with Yvh1 contain Rpl12 but lack both Mrt4 and P0. These results suggest a linear series of events in which Yvh1 binds to the pre-60S subunit to displace Mrt4. Subsequently, P0 loads onto the subunit to assemble the mature stalk, and Yvh1 is released. The initial assembly of the ribosome with Mrt4 may provide functional compartmentalization of ribosome assembly in addition to the spatial separation afforded by the nuclear envelope.

We previously showed that nuclear export of the large (60S) ribosomal subunit relies on Nmd3 in a Crm1-dependent manner. Recently the general mRNA export factor, the Mtr2/Mex67 heterodimer, was shown to act as an export receptor in parallel with Crm1. These observations raise the possibility that nuclear export of the 60S subunit in Saccharomyces cerevisiae requires multiple export receptors. Here, we show that the previously characterized 60S subunit biogenesis factor, Arx1, also acts as an export receptor for the 60S subunit. We found that deletion of ARX1 was synthetic lethal with nmd3 and mtr2 mutants and was synthetic sick with several nucleoporin mutants. Deletion of ARX1 led to accumulation of pre-60S particles in the nucleus that were enriched for Nmd3, Crm1, Mex67, and Mtr2, suggesting that in the absence of Arx1, 60S export is impaired even though the subunit is loaded with export receptors. Finally, Arx1 interacted with several nucleoporins in yeast two-hybrid as well as in vitro assays. These results show that Arx1 can directly bridge the interaction between the pre-60S particle and the NPC and thus is a third export receptor for the 60S subunit in yeast.

Developing a multiple functional wound dressing suitable for different stages of wound healing is important for patients with special wound such as burn or decubital ulcers. In this study, poly (vinyl alcohol) (PVA), dextran, and chitosan are integrated to produce ideal wound dressing where glutaraldehyde (GA) is used as the cross-linker. The result demonstrated that 6% PVA hydrogel with 0.25% chitosan was found to provide antimicrobial ability. The PVA/chitosan hydrogel combined with 4% dextran utilizing GA cross-linking also presents the high cell proliferation ability, which suggests that the hydrogel is potential as a wound dressing. In the following physical analyses, the addition of chitosan and dextran appeared to promote the thermostability, mechanical properties, water retention, and moisturizing ability in the PVA hydrogel. In conclusion, the PVA/chitosan/dextran hydrogel has promising potential such as high water content, antimicrobial property, and well cell proliferation, which can be applied to wound healing application.