High impact information on SAC3

• We show that overproduction of a sequence, termed CID, in the carboxy-terminal domain of the nuclear export factor Sac3 titrates Cdc31, causing a dominant-lethal phenotype and a block in spindle pole body (SPB) duplication [1].
• In vivo, Sac3p forms a stable complex with Thp1p, which was reported to function in transcription elongation [2].
• The mRNA export machinery requires the novel Sac3p-Thp1p complex to dock at the nucleoplasmic entrance of the nuclear pores [2].
• In addition to the 11 subdomains common to Snf1-like serine/threonine kinases, Sac3 and the plant kinases have two additional subdomains and a highly acidic C-terminal region [3].
• The role of Sac3 in the signal transduction system that regulates the responses of Chlamydomonas to sulfur limitation is discussed [3].

Biological context of SAC3

• In this report we further show that SAC3 function is required for normal progression of mitosis [4].
• SAC3 mutants showed a higher fraction of large-budded cells in culture, indicative of a cell cycle delay [4].
• The observation that SAC3 mutants lose chromosomes with higher frequency than wild-type is another indication for a mitotic defect in SAC3 mutants [4].
• Loss of SAC3 function results in a block in nuclear export of a nuclear export signal-containing reporter protein [5].
• Furthermore, we examined the act1-1 and the sac3 mutants for defects in polarized cell growth by FITC-Concanavalin A (Con A)-labelling [6].

Anatomical context of SAC3

• This finding suggests that SAC3 is involved, directly or indirectly, in microtubule function [4].
• In summary, our data indicate that SAC3 is involved in a process which affects both the actin cytoskeleton and mitosis [4].
• Sac3 is an mRNA export factor that localizes to cytoplasmic fibrils of nuclear pore complex [7].
• On sucrose density gradients Sac3p co-fractionated with the nuclear organelle markers examined [4].

Associations of SAC3 with chemical compounds

• The Saccharomyces cerevisiae LEP1/SAC3 gene is associated with leucine transport [8].
• Transformation of one such mutant, lep1, restored sensitivity to trifluoroleucine [8].
• Furthermore, we report that the mRNA export factor Sac3 is involved in this galactose-induced enrichment of GAL loci at the nuclear periphery [9].
• The deduced amino acid sequence of the Sac3 gene product is similar to the catalytic domain of the yeast Snf1 family of serine/threonine kinases and is therefore classified as a Snf1-related kinase (SnRK) [3].
• In contrast to its effect on arylsulfatase activity, Sac3 positively regulates the high-affinity sulfate transport system-the sac3 mutant is unable to fully induce high-affinity sulfate transport during sulfur limitation [3].

Regulatory relationships of SAC3

• A temperature-sensitive mutation (act1-1) in the essential actin gene of Saccharomyces cerevisiae can be suppressed by mutations in the SAC3 gene [6].

Other interactions of SAC3

• The original identification of SAC3 was based on the isolation of a mutant allele, sac3-1, that suppresses the temperature-sensitive growth defect of an actin mutant containing the allele act1-1 [8].
• Taken together, our data suggest that the novel Sac3p-Thp1p complex functions by docking the mRNP to specific nucleoporins at the nuclear entrance of the NPC [2].
• Altogether, our results suggest that Thp1p-Sac3p and Nab2p are functionally related heterogeneous nuclear ribonucleoproteins that define a further link between mRNA metabolism and transcription [10].
• Furthermore, Sac3p was enriched 10-fold in a nuclei preparation along with the nuclear protein Nop1p [4].

Analytical, diagnostic and therapeutic context of SAC3

• Immunoelectron microscopy analysis shows that Sac3 localizes exclusively to cytoplasmic fibrils of the NPC [7].

References