News & Comment

Transcriptionally silent sperm contains a variety of RNA fragments of both coding and non-coding transcripts. A recent article by Peng and colleagues reveals several new families of small RNAs enriched in sperm, which are derived from the same locus as tRNAs. The finding of these short fragments of tRNA in the sperm raises once again the question of the possible function(s) of such a miniaturized form of information carried by the spermatozoon.

In a recent paper published in Nature, Carrieri et al. have identified in mouse a neuron-specific antisense lncRNA transcribed in the opposite strand of Uchl1 mRNA. Antisense Uchl1 specifically promotes the translation of UCHL1 under rapamycin treatment. To do so, the lncRNA only requires a SINEB2 repeat and a small region with sequence complementarity to the regulated mRNA.

T lymphocytes express clonal receptors, called T cell receptors (TCRs), which specifically recognize antigens presented in combination with major histocompatibility molecules (MHC). To date, T cell antigens can be broadly categorized into two classes: peptides and lipids. A recent paper published in Nature by Kjer-Nielsen and colleagues reveals that a unique population of T lymphocytes expresses TCRs that recognize a completely new and unexpected class of antigens, vitamin metabolites.

Functional human cardiomyocytes hold great promise in cell transplantation-based therapy to treat many heart diseases. To meet this devastating and clinical need, researchers are infatuated with developing novel technologies and methodologies to efficiently generate cardiomyocytes through either stem cell differentiation or cell lineage transdifferentiation. Though exciting progress has been made, challenges remain to be addressed before the translation from bench side to bed side can be fulfilled.

An abundance of long non-coding RNA (lncRNA) present in most species from yeast to human are involved in transcriptional regulation, dosage compensation and imprinting. This underscores the importance of lncRNA as functional RNA despite the fact that they do not produce proteins. Two recent papers in Cell have demonstrated that transcription of the non-conserved lncRNAs, but not the RNAs themselves, is necessary to introduce co-transcriptional regulatory histone marks to regulate gene expression.

Repair of double-strand breaks by homologous recombination requires Repair of double-strand breaks by homologous recombination requires 5′-3′ resection of the DNA ends to create 3′ single-stranded DNA tails. While much progress has been made in identifying the proteins that directly participate in end resection, how this process occurs in the context of chromatin is not well understood. Two papers in Nature report that Fun30, a poorly characterized member of the Swi2/Snf2 family of chromatin remodelers, plays a role in end processing by facilitating the Exo1 and Sgs1-Dna2 resection pathways.

The significant correlation between disease aggressiveness and the gene and protein structures of the B-cell receptors (BCRs) expressed on chronic lymphocytic leukemia (CLL) cells, together with the evidence for chronic activation of the BCR pathway, have led to the hypothesis that this leukemia initiates and progresses by selecting normal B lymphocytes reactive with a restricted set of (auto)antigens. A study recently published in Nature identified a novel signal-initiating interaction between the third complementary determining region of the IG heavy chain variable domain (HCDR3) and an epitope in the second framework region (FR2) that appears to be unique to CLL B cells and that calls into question the need for classical antigen binding in the activation and expansion of the leukemic cells. These findings are discussed in the context of available information about the antigen reactivity of CLL B cells and its potential role in clonal survival and drive.

Human immunodeficiency virus type 1 (HIV-1) is the cause of AIDS. In recent years it has emerged that cellular interferon-stimulated genes (ISG), play important roles in cell-intrinsic restriction of HIV replication. A publication now describes a novel strategy employed by HIV-infected cells to restrict viral replication, which involves inhibition of viral mRNA translation by the ISG Schlafen 11.

Blood transfusion medicine requires a constant supply of platelets, which is now totally donor dependent. Recent advances in the generation of platelets in vitro through megakaryocytes (MKs) may provide protocols not only via pluripotent stem cells, including induced pluripotent stem cells (iPSCs) and embryonic stem cells (ESCs), but also via induced MKs (iMKs). For the first time, mouse and human fibroblasts are successfully transdifferentiated into iMKs by the introduction of three factors, p45NF-E2, Maf G, and Maf K.