ILDR2 Is a Novel B7-like Protein That Negatively Regulates T Cell Responses.

The B7-like protein family members play critical immunomodulatory roles and constitute attractive targets for the development of novel therapies for human diseases. We identified Ig-like domain-containing receptor (ILDR)2 as a novel B7-like protein with robust T cell inhibitory activity, expressed in immune cells and in immune-privileged and inflamed tissues. A fusion protein, consisting of ILDR2 extracellular domain with an Fc fragment, that binds to a putative counterpart on activated T cells showed a beneficial effect in the collagen-induced arthritis model and abrogated the production of proinflammatory cytokines and chemokines in autologous synovial-like cocultures of macrophages and cytokine-stimulated T cells. Collectively, these findings point to ILDR2 as a novel negative regulator for T cells, with potential roles in the development of immune-related diseases, including autoimmunity and cancer.

DTIE, a novel core promoter element that directs start site selection in TATA-less genes.

The transcription start site (TSS) determines the length and composition of the 5' UTR and therefore can have a profound effect on translation. Yet, little is known about the mechanism underlying start site selection, particularly from promoters lacking conventional core elements such as TATA-box and Initiator. Here we report a novel mechanism of start site selection in the TATA- and Initiator-less promoter of miR-22, through a strictly localized downstream element termed DTIE and an upstream distal element. Changing the distance between them reduced promoter strength, altered TSS selection and diminished Pol II recruitment. Biochemical assays suggest that DTIE does not serve as a docking site for TFIID, the major core promoter-binding factor. TFIID is recruited to the promoter through DTIE but is dispensable for TSS selection. We determined DTIE consensus and found it to be remarkably prevalent, present at the same TSS downstream location in ≈20.8% of human promoters, the vast majority of which are TATA-less. Analysis of DTIE in the tumor suppressor p53 confirmed a similar function. Our findings reveal a novel mechanism of transcription initiation from TATA-less promoters.

Disparity between microRNA levels and promoter strength is associated with initiation rate and Pol II pausing.

MicroRNAs are transcribed by RNA polymerase II but the transcriptional features influencing their synthesis are poorly defined. Here we report that a TATA box in microRNA and protein-coding genes is associated with increased sensitivity to slow RNA polymerase II. Promoters driven by TATA box or NF-κB elicit high re-initiation rates, but paradoxically lower microRNA levels. MicroRNA synthesis becomes more productive by decreasing the initiation rate, but less productive when the re-initiation rate increases. This phenomenon is associated with a delay in miR-146a induction by NF-κB. Finally, we demonstrate that microRNAs are remarkably strong pause sites. Our findings suggest that lower efficiency of microRNA synthesis directed by TATA box or NF-κB is a consequence of frequent transcription initiations that lead to RNA polymerase II crowding at pause sites, thereby increasing the chance of collision and premature termination. These findings highlight the importance of the transcription initiation mechanism for microRNA synthesis, and have implications for TATA-box promoters in general.