Catalysis of the reaction: a 3-beta-hydroxyl sterol + NADP+ = a 3-keto sterol + NADPH + H(+).

Catalysis of the reaction: (S)-2,3-epoxysqualene = lanosterol. This is a cyclization reaction that forms the sterol nucleus.

Catalysis of the formation of the C-22(23) double bond in the sterol side chain. An example reaction: 5,7,24(28)-ergostatrienol + O2 + NADPH = 5,7,22,24(28)-ergostatetraenol + 2 H2O + NADP+.

Catalysis of the introduction of a double bond into a sterol molecule.

Catalysis of an oxidation-reduction (redox) reaction in which hydrogen or electrons are transferred from each of two donors, and molecular oxygen is reduced to two molecules of water.

Catalysis of the reaction which results in unsaturation at C-7 in the B ring of sterols.

Catalysis of the reaction: 5,7,24(28)-ergostatrienol + O2 + NADPH = 5,7,22,24(28)-ergostatetraenol + 2 H2O + NADP+.

The aggregation, arrangement and bonding together of a spliceosomal complex, a ribonucleoprotein apparatus that catalyzes nuclear mRNA splicing via transesterification reactions.

Catalysis of the reaction: ergosterol + NADP(+) = ergosta-5,7,22,24(24(1))-tetraen-3beta-ol + H(+) + NADPH.

A spliceosomal complex that is formed by association of the U1 snRNP with the 5' splice site of an unspliced intron in an RNA transcript.

Any spliceosomal complex that forms during the splicing of a messenger RNA primary transcript to excise an intron that has canonical consensus sequences near the 5' and 3' ends.

The formation of a tri-snRNP complex containing U4 and U6 (or U4atac and U6atac) snRNAs and U5 snRNAs and associated proteins. This includes reannealing of U4 and U6 (or U4atac and U6atac) snRNAs released from previous rounds of splicing to reform the U4/U6 snRNP (or U4atac/U6atac snRNP) as well as the subsequent association of the U5 snRNP with the U4/U6 snRNP (or U4atac/U6atac snRNP) to form a tri-snRNP that is ready to reassemble into another spliceosome complex.

The cell cycle phase which follows diplotene during prophase I of meiosis, the separation of homologous chromosomes is complete and crossing over has occurred.

A meiotic cell cycle phase prior to a during which some part of meiosis I nuclear division or the proceeding cytokinesis occurs.

A network of small fibers that surrounds the centrioles in cells; contains the microtubule nucleating activity of the centrosome.

The cell cycle phase which follows pachytene during prophase I of meiosis, during which the homologous chromosomes begin to separate and the synaptonemal complex dissolves.

The cell cycle phase which follows leptotene during prophase I of meiosis, and during which each chromosome pairs with its homolog; the two become aligned and crossing over may occur.

The cell cycle phase which follows zygotene during prophase I of meiosis, and during which crossing over occurs between a chromatid in one partner and another chromatid in the homologous chromosome.

The cell cycle phase in higher eukaryotes which follows mitotic prophase and during which the nuclear envelope is disrupted and breaks into membrane vesicles, and the spindle microtubules enter the nuclear region. Kinetochores mature on each centromere and attach to some of the spindle microtubules. Kinetochore microtubules begin the process of aligning chromosomes in one plane halfway between the poles.