PEGylation of lysine residues improves the proteolytic stability of fibronectin while retaining biological activity

Excessive proteolysis of fibronectin (FN) impairs tissue repair in chronic wounds. Since FN is essential in wound healing, our goal is to improve its proteolytic stability and at the same time preserve its biological activity. We have previously shown that reduced FN conjugated with polyethylene glycol (PEG) at cysteine residues is more proteolytically stable than native FN. Cysteine‐PEGylated FN supported cell adhesion and migration to the same extent as native FN. However, unlike native FN, cysteine‐PEGylated FN was not assembled into an extracellular matrix (ECM) when immobilized. Here, we present an alternative approach in which FN is preferentially PEGylated at lysine residues using different molecular weight PEGs. We show that lysine PEGylation does not perturb FN secondary structure. PEG molecular weight, from 2 to 10 kDa, positively correlates with FN–PEG proteolytic stability. Cell adhesion, cell spreading, and gelatin binding decrease with increasing molecular weight of PEG. The 2‐kDa FN–PEG conjugate shows comparable cell adhesion to native FN and binds gelatin. Moreover, immobilized FN–PEG is assembled into ECM fibrils. In summary, lysine PEGylation of FN can be used to stabilize FN against proteolytic degradation with minimal perturbation to FN structure and retained biological activity.     

Precise centromere mapping using a combination of repeat junction markers and chromatin immunoprecipitation-polymerase chain reaction

Centromeres are difficult to map even in species where genetic resolution is excellent. Here we show that junctions between repeats provide reliable single-copy markers for recombinant inbred mapping within centromeres and pericentromeric heterochromatin. Repeat junction mapping was combined with anti-CENH3-mediated ChIP to provide a definitive map position for maize centromere 8.     

Distribution and diversity of palms in a tropical biodiversity hotspot (Thailand) assessed by species distribution modeling

Species distribution modeling has been widely used to address questions related to ecology, biogeography and species conservation on global and regional scales. Here, we study palms (Arecaceae) in a tropical biodiversity hotspot (Thailand) using species distribution modeling to assess range‐limiting factors and estimate distribution and diversity patterns based on a comprehensive compilation of occurrence records. We focused on palms as a model group due to their key‐stone importance for ecosystem functioning and socio‐economics. Different combinations of climatic, non‐climatic environmental and spatial predictors were used. The most accurate models as indicated by the ‘area under the receiver operating characteristic curve’ (AUC) statistic were those that combined all predictors. The four strongest single predictors of palm species distributions were, in decreasing order of importance, 1) latitude, 2) precipitation of driest quarter, 3) annual precipitation, and 4) minimum temperature of the coldest month, suggesting rainfall patterns and latitudinal spatial constraints as the main range determinants. Overlaying the predicted distributions revealed that potential palm hotspots are situated in the provinces of Satun and Yala in southern Thailand where vast areas remain relatively open to the discovery of new palm records and perhaps even new species.     

Ca2+/Calmodulin-dependent Protein Kinase IIα (αCaMKII) Controls the Activity of the Dopamine Transporter: IMPLICATIONS FOR ANGELMAN SYNDROME

The dopamine transporter (DAT) is a crucial regulator of dopaminergic neurotransmission, controlling the length and brevity of dopaminergic signaling. DAT is also the primary target of psychostimulant drugs such as cocaine and amphetamines. Conversely, methylphenidate and amphetamine are both used clinically in the treatment of attention-deficit hyperactivity disorder and narcolepsy. The action of amphetamines, which induce transport reversal, relies primarily on the ionic composition of the intra- and extracellular milieus. Recent findings suggest that DAT interacting proteins may also play a significant role in the modulation of reverse dopamine transport. The pharmacological inhibition of the serine/threonine kinase αCaMKII attenuates amphetamine-triggered DAT-mediated 1-methyl-4-phenylpyridinium (MPP(+)) efflux. More importantly, αCaMKII has also been shown to bind DAT in vitro and is therefore believed to be an important player within the DAT interactome. Herein, we show that αCaMKII co-immunoprecipitates with DAT in mouse striatal synaptosomes. Mice, which lack αCaMKII or which express a permanently self-inhibited αCaMKII (αCaMKII(T305D)), exhibit significantly reduced amphetamine-triggered DAT-mediated MPP(+) efflux. Additionally, we investigated mice that mimic a neurogenetic disease known as Angelman syndrome. These mice possess reduced αCaMKII activity. Angelman syndrome mice demonstrated an impaired DAT efflux function, which was comparable with that of the αCaMKII mutant mice, indicating that DAT-mediated dopaminergic signaling is affected in Angelman syndrome.     

The plant glycosyltransferase clone collection for functional genomics

The glycosyltransferases (GTs) are an important and functionally diverse family of enzymes involved in glycan and glycoside biosynthesis. Plants have evolved large families of GTs which undertake the array of glycosylation reactions that occur during plant development and growth. Based on the Carbohydrate‐Active enZymes (CAZy) database, the genome of the reference plant Arabidopsis thaliana codes for over 450 GTs, while the rice genome (Oryza sativa) contains over 600 members. Collectively, GTs from these reference plants can be classified into over 40 distinct GT families. Although these enzymes are involved in many important plant specific processes such as cell‐wall and secondary metabolite biosynthesis, few have been functionally characterized. We have sought to develop a plant GTs clone resource that will enable functional genomic approaches to be undertaken by the plant research community. In total, 403 (88%) of CAZy defined Arabidopsis GTs have been cloned, while 96 (15%) of the GTs coded by rice have been cloned. The collection resulted in the update of a number of Arabidopsis GT gene models. The clones represent full‐length coding sequences without termination codons and are Gateway^® compatible. To demonstrate the utility of this JBEI GT Collection, a set of efficient particle bombardment plasmids (pBullet) was also constructed with markers for the endomembrane. The utility of the pBullet collection was demonstrated by localizing all members of the Arabidopsis GT14 family to the Golgi apparatus or the endoplasmic reticulum (ER). Updates to these resources are available at the JBEI GT Collection website http://www.addgene.org/ .     

Visualization of RNA-protein interactions in living cells: FMRP and IMP1 interact on mRNAs

Protein expression depends significantly on the stability, translation efficiency and localization of mRNA. These qualities are largely dictated by the RNA-binding proteins associated with an mRNA. Here, we report a method to visualize and localize RNA-protein interactions in living mammalian cells. Using this method, we found that the fragile X mental retardation protein (FMRP) isoform 18 and the human zipcode-binding protein 1 ortholog IMP1, an RNA transport factor, were present on common mRNAs. These interactions occurred predominantly in the cytoplasm, in granular structures. In addition, FMRP and IMP1 interacted independently of RNA. Tethering of FMRP to an mRNA caused IMP1 to be recruited to the same mRNA and resulted in granule formation. The intimate association of FMRP and IMP1 suggests a link between mRNA transport and translational repression in mammalian cells.