Essentiality of Sis1, a J-domain protein Hsp70 cochaperone, can be overcome by Tti1, a specialized PIKK chaperone

J-domain protein cochaperones drive much of the functional diversity of Hsp70-based chaperone systems. Sis1 is the only essential J-domain protein of the cytosol/nucleus of Saccharomyces cerevisiae. Why it is required for cell growth is not understood, nor is how critical its role in regulation of heat shock transcription factor 1 (Hsf1). We report that single residue substitutions in Tti1, a component of the heterotrimeric TTT complex, a specialized chaperone system for phosphatidylinositol 3-kinase-related kinase (PIKK) proteins, allow growth of cells lacking Sis1. Upon depletion of Sis1, cells become hypersensitive to rapamycin, a specific inhibitor of TORC1 kinase. In addition, levels of the three essential PIKKs (Mec1, Tra1, and Tor2), as well as Tor1, decrease upon Sis1depletion. Overexpression of Tti1 allows growth, without an increase in the other subunits of the TTT complex, Tel2 and Tti2, suggesting that it can function independent of the complex. Cells lacking Sis1, with viability supported by Tti1 suppressor, substantially upregulate some, but not all, heat shock elements activated by Hsf1. Together, our results suggest that Sis1 is required as a cochaperone of Hsp70 for the folding/maintenance of PIKKs making Sis1 an essential gene, and its requirement for Hsf1 regulation is more nuanced than generally appreciated.

Differential expression of E2F transcription factor 1 in triple negative breast cancer.

Women diagnosed with triple negative breast cancer can benefit neither from endocrine therapy nor from HER2-targeted therapies (1). We mined published microarray datasets (2, 3) to determine in an unbiased fashion and at the systems level genes most differentially expressed in the primary tumors of patients with breast cancer. We report here significant differential expression of the gene encoding E2F transcription factor 1, E2F1, when comparing the tumor cells of patients with triple negative breast cancer to normal mammary ductal cells (2). E2F1 was also differentially expressed in bulk tumor in human breast cancer (3). E2F1 mRNA was present at significantly increased quantities in TNBC tumor cells relative to normal mammary ductal cells. Analysis of human survival data revealed that expression of E2F1 in primary tumors of the breast was correlated with distant metastasis-free survival in patients with luminal A type cancer, while within triple negative breast cancer, primary tumor expression of E2F1 was correlated with recurrence-free survival in patients with mesenchymal stem-like subtype disease. E2F1 may be of relevance to initiation, maintenance or progression of triple negative breast cancers.

Phenotype from SAMD9 Mutation at 7p21.1 Appears Attenuated by Novel Compound Heterozygous Variants at RUNX2 and SALL1

Sterile α motif domain-containing protein 9 (SAMD9) is a regulatory protein centrally involved in cell proliferation and apoptosis. Mapped to 7p21.1, variants in SAMD9 have been reported in <50 pediatric cases worldwide, typically with early lethality. Germline gain-of-function SAMD9 variants are associated with MIRAGE syndrome (myelodysplasia, infection, restricted growth, adrenal hypoplasia, genital anomalies, and enteropathy). Spalt like transcription factor 1 (SALL1) is a zinc finger transcriptional repressor located at 16q12.1 where only two transcript variants in SALL1 are known. RUNX2 (6p21.1) encodes a nuclear protein with a Runt DNA-binding domain critical for osteoblastic differentiation, skeletal morphogenesis, and serves as a scaffold for nucleic acids and regulatory factors involved in skeletal gene expression. RUNX2 and SALL1 are thus both “master regulators” of tissue organization and embryo development. Here, we describe exome sequencing and copy number variants in two previously unknown mutations—R824Q in SAMD9, and Q253H in SALL1. A multiexon 3′ terminal duplication of RUNX2 not previously encountered is also reported. This is the first known phenotype assessment for an intersection of all three variants in a healthy 46,XX adult. Focusing on developmental progress, ultrastructural renal anatomy, and selected reproductive aspects, we describe this unique genotype diagnosed incidentally during coronavirus disease 2019 (COVID-19) illness. Individually, disruption in SAMD9, RUNX2, or SALL1 would be expected to give a bleak prognosis. However, this variant convergence appears to dampen severe pathology perhaps by cross-gene silencing of effects normally deleterious when such changes occur alone.

miRNA target prediction of avian Z-linked DMRT1 gene during sex determination in chicken (G. Gallus)

Sex determination in dimorphic animal, such as chicken (G. Gallus), is controlled by the expression of doublesex and mab-3 related transcription factor 1 (DMRT1) gene. This gene act as sex determination switch by critically needed for testis differentiation and as antagonist of ovarian development. miRNA, is belongs to short noncoding RNA which modulate gene expression in specific or board targeted genes. This study was aimed to predict miRNA(s) candidate targeted to DMRT1 expression in chicken. In silico method was employed to mining miRNA targeted to DMRT1 using three online databases namely miRDB, TargetScan, and microT-CDS. Following prediction, clustering was performed to select common miRNA(s) in minimal two databases for gene ontology (GO) analysis. Totally 78 miRNAs were targeted to DMRT1 3’UTR, and eight miRNA(s) were found in minimal two databases. The GO analysis found seven distinct biological functions in membrane, cytoplasm, protein binding, nucleus, integral component of membrane and molecular function, and all are related to the cell growth namely cell proliferation. According to the result, it shows the possibility to use selected candidate of miRNA(s) targeted to DMRT1 to reveal the sex determination mechanism at early stage of chicken development.