In this task, you are given an abstract of article. Your task is to generate title for this article. Preferred titles are under thirty words.

Q: Ubiquitylation is a reversible protein modification that is implicated in many cellular functions. Recently, much progress has been made in the characterization of a superfamily of isopeptidases that remove ubiquitin: the deubiquitinases (DUBs; also known as deubiquitylating or deubiquitinating enzymes). Far from being uniform in structure and function, these enzymes display a myriad of distinct mechanistic features. The small number (<100) of DUBs might at first suggest a low degree of selectivity; however, DUBs are subject to multiple layers of regulation that modulate both their activity and their specificity. Due to their wide-ranging involvement in key regulatory processes, these enzymes might provide new therapeutic targets.

A: Breaking the chains: structure and function of the deubiquitinases
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Q: Haematopoietic stem cells (HSCs) and their subsequent progenitors produce blood cells, but the precise nature and kinetics of this production is a contentious issue. In one model, lymphoid and myeloid production branch after the lymphoid-primed multipotent progenitor (LMPP), with both branches subsequently producing dendritic cells. However, this model is based mainly on in vitro clonal assays and population-based tracking in vivo, which could miss in vivo single-cell complexity. Here we avoid these issues by using a new quantitative version of 'cellular barcoding' to trace the in vivo fate of hundreds of LMPPs and HSCs at the single-cell level. These data demonstrate that LMPPs are highly heterogeneous in the cell types that they produce, separating into combinations of lymphoid-, myeloid- and dendritic-cell-biased producers. Conversely, although we observe a known lineage bias of some HSCs, most cellular output is derived from a small number of HSCs that each generates all cell types. Crucially, in vivo analysis of the output of sibling cells derived from single LMPPs shows that they often share a similar fate, suggesting that the fate of these progenitors was imprinted. Furthermore, as this imprinting is also observed for dendritic-cell-biased LMPPs, dendritic cells may be considered a distinct lineage on the basis of separate ancestry. These data suggest a 'graded commitment' model of haematopoiesis, in which heritable and diverse lineage imprinting occurs earlier than previously thought.

A: Diverse and heritable lineage imprinting of early haematopoietic progenitors
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Q: Human embryonic stem (ES) cell lines that have the ability to self-renew and differentiate into specific cell types have been established. The molecular mechanisms for self-renewal and differentiation, however, are poorly understood. We determined the transcriptome profiles for two proprietary human ES cell lines (HES3 and HES4, ES Cell International), and compared them with murine ES cells and other human tissues. Human and mouse ES cells appear to share a number of expressed gene products although there are numerous notable differences, including an inactive leukemia inhibitory factor pathway and the high preponderance of several important genes like POU5F1 and SOX2 in human ES cells. We have established a list of genes comprised of known ES-specific genes and new candidates that can serve as markers for human ES cells and may also contribute to the "stemness" phenotype. Of particular interest was the downregulation of DNMT3B and LIN28 mRNAs during ES cell differentiation. The overlapping similarities and differences in gene expression profiles of human and mouse ES cells provide a foundation for a detailed and concerted dissection of the molecular and cellular mechanisms governing their pluripotency, directed differentiation into specific cell types, and extended ability for self-renewal.

A:
The transcriptome profile of human embryonic stem cells as defined by SAGE.
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