A tetramer of BCL11A is required for stable protein production and fetal hemoglobin silencing.

Down-regulation of BCL11A protein reverses the fetal (HbF, αγ) to adult (HbA, αβ) hemoglobin switch and is exploited in gene-based therapy for hemoglobin disorders. Because of reliance on ex vivo cell manipulation and marrow transplant, such therapies cannot lessen disease burden. To develop new small-molecule approaches, we investigated the state of BCL11A protein in erythroid cells.

Structural insights into the DNA-binding mechanism of BCL11A: The integral role of ZnF6.

The transcription factor BCL11A is a critical regulator of the switch from fetal hemoglobin (HbF: αγ) to adult hemoglobin (HbA: αβ) during development. BCL11A binds at a cognate recognition site (TGACCA) in the γ-globin gene promoter and represses its expression. DNA-binding is mediated by a triple zinc finger domain, designated ZnF456.

Structural Insights into the DNA-Binding Mechanism of BCL11A: The Integral Role of ZnF6.

The transcription factor BCL11A is a critical regulator of the switch from fetal hemoglobin (HbF: α γ ) to adult hemoglobin (HbA: α β ) during development. BCL11A binds at a cognate recognition site (TGACCA) in the γ-globin gene promoter and represses its expression. DNA-binding is mediated by a triple zinc finger domain, designated ZnF456.

Evolution of nanobodies specific for BCL11A.

Transcription factors (TFs) control numerous genes that are directly relevant to many human disorders. However, developing specific reagents targeting TFs within intact cells is challenging due to the presence of highly disordered regions within these proteins. Intracellular antibodies offer opportunities to probe protein function and validate therapeutic targets.

Phage AcrIIA2 DNA Mimicry: Structural Basis of the CRISPR and Anti-CRISPR Arms Race.

CRISPR-Cas (clustered regularly interspaced short palindromic repeats-CRISPR-associated proteins) systems provide prokaryotic cells with adaptive immunity against invading bacteriophages. Bacteriophages counteract bacterial responses by encoding anti-CRISPR inhibitor proteins (Acr). However, the structural basis for their inhibitory actions remains largely unknown.

Molecular mechanism of directional CTCF recognition of a diverse range of genomic sites.

CTCF, a conserved 3D genome architecture protein, determines proper genome-wide chromatin looping interactions through directional binding to specific sequence elements of four modules within numerous CTCF-binding sites (CBSs) by its 11 zinc fingers (ZFs). Here, we report four crystal structures of human CTCF in complex with CBSs of the protocadherin (Pcdh) clusters. We show that directional CTCF binding to cognate CBSs of the Pcdh enhancers and promoters is achieved through inserting its ZF3, ZFs 4-7, and ZFs 9-11 into the major groove along CBSs, resulting in a sequence-specific recognition of module 4, modules 3 and 2, and module 1, respectively; and ZF8 serves as a spacer element for variable distances between modules 1 and 2.

Two Distant Catalytic Sites Are Responsible for C2c2 RNase Activities.

C2c2, the effector of type VI CRISPR-Cas systems, has two RNase activities-one for cutting its RNA target and the other for processing the CRISPR RNA (crRNA). Here, we report the structures of Leptotrichia shahii C2c2 in its crRNA-free and crRNA-bound states. While C2c2 has a bilobed structure reminiscent of all other Class 2 effectors, it also exhibits different structural characteristics.

C2c1-sgRNA Complex Structure Reveals RNA-Guided DNA Cleavage Mechanism.

C2c1 is a type V-B CRISPR-Cas system dual-RNA-guided DNA endonuclease. Here, we report the crystal structure of Alicyclobacillus acidoterrestris C2c1 in complex with a chimeric single-molecule guide RNA (sgRNA). AacC2c1 exhibits a bi-lobed architecture consisting of a REC and NUC lobe.

Structural and Mechanistic Basis of PAM-Dependent Spacer Acquisition in CRISPR-Cas Systems.

Bacteria acquire memory of viral invaders by incorporating invasive DNA sequence elements into the host CRISPR locus, generating a new spacer within the CRISPR array. We report on the structures of Cas1-Cas2-dual-forked DNA complexes in an effort toward understanding how the protospacer is sampled prior to insertion into the CRISPR locus. Our study reveals a protospacer DNA comprising a 23-bp duplex bracketed by tyrosine residues, together with anchored flanking 3' overhang segments.

Constitutive expression, purification and characterisation of pectin methylesterase from Aspergillus niger in Pichia pastoris for potential application in the fruit juice industry.

Background: Pectin methylesterase (PME) catalyses the hydrolysis of the methyl ester of pectin, yielding free carboxyl groups and methanol. PME is widely used in the food, cosmetic and pharmaceutical industries.

Results: PME from Aspergillus niger was constitutively expressed to a high level in the yeast Pichia pastoris.