Forced homo-oligomerization of RARα leads to transformation of primary hematopoietic cells

SummaryAlmost 100% of APL patients carry chimeric transcripts encoding truncated RARα fused to homo-oligomerization domains from partner proteins. To gain further insights into the cellular transformation mechanisms mediated by RARα fusion proteins, thorough structure/function analyses have been performed and identified the POZ homo-oligomerization domain as the minimal transformation domain that is necessary and sufficient for PLZF-RARα-mediated in vitro transformation of primary hematopoietic cells. A transformation-incompetent PLZF-RARα mutant defective in homo-oligomerization but not corepressor interaction could be rescued by synthetic FKBP-oligomerization domains. Furthermore, an artificial FKBP-RARα construct not only mimicked various biochemical properties of bona fide RARα fusion proteins but also mediated an ATRA-dependent transformation. Taken together, these findings endorse an oligomerization-dependent mechanism for RARα-mediated transformation and suggest a potential avenue for molecular therapy

China

Economic development processes in post-1949 China can be divided into two periods. In the first, 1950-70, the economy was extensively and intensively controlled by the state with a priority for developing heavy industries. In the second, since the 80s and known as the \u27reform period,\u27 the Chinese economy has increasingly been integrated with the world economy and relying on light (rural) industries as the prime motor of economic growth. Yet, in both these periods, Chinese policymakers shared the same \u27developmental\u27 philosophy in which social costs, that is the reproduction costs of human labour and nature, are largely ignored. The following is a critical sketch of government policies and their impact on the domestic population in these two periods

Human COL2A1-directed SV40 T antigen expression in transgenic and chimeric mice results in abnormal skeletal development

The ability of SV40 T antigen to cause abnormalities in cartilage development in transgenic mice and chimeras has been tested. The cis- regulatory elements of the COL2A1 gene were used to target expression of SV40 T antigen to differentiating chondrocytes in transgenic mice and chimeras derived from embryonal stem (ES) cells bearing the same transgene. The major phenotypic consequences of transgenic (pAL21) expression are malformed skeleton, disproportionate dwarfism, and perinatal/neonatal death. Expression of T antigen was tissue specific and in the main characteristic of the mouse α1(II) collagen gene. Chondrocyte densities and levels of α1(II) collagen mRNAs were reduced in the transgenic mice. Islands of cells which express cartilage characteristic genes such as type IIB procollagen, long form α1(IX) collagen, α2(XI) collagen, and aggrecan were found in the articular and growth cartilages of pAL21 chimeric fetuses and neonates. But these cells, which were expressing T antigen, were not properly organized into columns of proliferating chondrocytes. Levels of α1(II) collagen mRNA were reduced in these chondrocytes. In addition, these cells did not express type X collagen, a marker for hypertrophic chondrocytes. The skeletal abnormality in pAL21 mice may therefore be due to a retardation of chondrocyte maturation or an impaired ability of chondrocytes to complete terminal differentiation and an associated paucity of some cartilage matrix components.published_or_final_versio

The central policy unit in the governance of Hong Kong : a study of institutional dynamics

published_or_final_versionPolitics and Public AdministrationMasterMaster of Public Administratio

Functional connexin35 increased in the myopic chicken retina.

Our previous research showed that increased phosphorylation of connexin (Cx)36 indicated extended  coupling of AII amacrine cells (ACs) in the rod-dominant mouse myopic retina. This research will determine whether phosphorylation at serine 276 of Cx35-containing gap junctions increased in the myopic chicken, whose retina is cone-dominant. Refractive errors and ocular biometric dimensions of 7-days-old chickens were determined following 12 h and 7 days induction of myopia by a -10D lens. The expression pattern and size of Cx35-positive plaques were examined in the early (12 h) and compensated stages (7 days) of lens-induced myopia (LIM). At the same time, phosphorylation at serine 276 (functional assay) of Cx35 in strata 5 (S5) of the inner plexiform layer was investigated. The axial length of the 7 days LIM eyes was significantly longer than that of non-LIM controls (P < 0.05). Anti-phospho-Ser276 (Ser276-P)-labeled plaques were significantly increased in LIM retinas at both 12 h and 7 days. The density of Ser276-P of Cx35 was observed to increase after 12 h LIM. In the meanwhile, the areas of existing Cx35 plaques did not change. As there was more phosphorylation of connexin35 at Ser276 at both the early and late stages (12 h) and 7 days of LIM chicken retinal activity, the coupling with ACs could be increased in myopia development of the cone-dominated chicken retina

Pegylated derivatives of recombinant human arginase (rhArg1) for sustained in vivo activity in cancer therapy: preparation, characterization and analysis of their pharmacodynamics in vivo and in vitro and action upon hepatocellular carcinoma cell (HCC)

<p>Abstract</p> <p>Background</p> <p>Protein used in medicine, e.g. interferon, are immunogenic and quickly broken down by the body. Pegylation is a recognized way of preserving their integrity and reducing immune reactions, and works well with enzymes used to degrade amino acids, a recent focus of attention in controlling cancer growth. Of the two arginine-degrading enzymes being explored clinically, arginine deiminase is a decidedly foreign mycoplasm-derived enzyme, whereas human arginase 1 is a native liver enzyme. Both have been pegylated, the former with adjuncts of 20 kD, the latter with 5 kD PEG. Pegylation is done by several different methods, not all of which are satisfactory or desirable.</p> <p>Methods</p> <p>The preparation of novel polyethylene glycol (PEG) derivatives for modifying proteins is described, but directed specifically at pegylation of recombinant human arginase 1 (rhArg1). rhArg1 expressed in <it>Escherichia coli </it>was purified and coupled in various ways with 5 different PEG molecules to compare their protective properties and the residual enzyme activity, using hepatocellular cell lines both in vitro and in vivo.</p> <p>Results</p> <p>Methoxypolyethylene glycol-succinimidyl propionate (mPEG-SPA 5,000) coupled with very high affinity under mild conditions. The resulting pegylated enzyme (rhArg1-peg_{5,000 mw}) had up to 6 PEG chains of 5K length which not only protected it from degradation and any residual immunogenicity, but most importantly let it retain >90% of its native catalytic activity. It remained efficacious in depleting arginine in rats after a single ip injection of 1,500 U of the conjugate as the native enzyme, plasma arginine falling to >0.05 μM from ~170 μM within 20 min and lasting 6 days. The conjugate had almost the same efficacy as unpegylated rhArg1 on 2 cultured human liver cancer (HCC) cell lines. It was considerably more effective than 4 other pegylated conjugates prepared.</p> <p>Conclusion</p> <p>Valuable data on the optimization of the pegylation procedure and choice of ligand that best stabilizes the enzyme arginase 1 are presented, a protocol that should equally fit many other enzymes and proteins. It is a long lasting arginine-depleting enzyme in vivo which will greatly improve its use in anti-cancer therapy.</p

Hematopoietic stem cell quiescence and DNA replication dynamics maintained by the resilient β-catenin/Hoxa9/Prmt1 axis

Maintenance of quiescence and DNA replication dynamics are two paradoxical requirements for the distinct states of dormant and active hematopoietic stem cells (HSCs), which are required to preserve the stem cell reservoir and replenish the blood cell system in response to hematopoietic stress respectively. Here, we show that key self-renewal factors, β-catenin or Hoxa9, largely dispensable for HSC integrity in fact have dual functions in maintaining quiescence and enabling efficient DNA replication fork dynamics to preserve the functionality of hematopoietic stem and progenitor cells (HSPCs). While β-catenin or Hoxa9 single knockout (KO) exhibited mostly normal hematopoiesis, their co-inactivation led to severe hematopoietic defects stemmed from aberrant cell cycle, DNA replication and damage in HSPCs. Mechanistically, β-catenin and Hoxa9 function in a compensatory manner to sustain key transcriptional programs that converge on the pivotal downstream target and epigenetic modifying enzyme, Prmt1, which protects the quiescent state and ensures an adequate supply of DNA replication and repair factors to maintain robust replication fork dynamics. Inactivation of Prmt1 phenocopied both cellular and molecular phenotypes of β-catenin/Hoxa9 combined KO, which at the same time could also be partially rescued by Prmt1 expression. The discovery of the highly resilient β-catenin/Hoxa9/Prmt1 axis in protecting both quiescence and DNA replication dynamics essential for HSCs at different key states provides not only novel mechanistic insights into their intricate regulation but also a potential tractable target for therapeutic intervention