| Topic | Key finding | Quantitative / mechanistic details | Evidence scope | Key citations (URL; date) |
|---|---|---|---|---|
| Identity & core function | **SAS3 (UniProt P34218; YBL052C)** in *Saccharomyces cerevisiae* is the **MYST-family catalytic histone acetyltransferase** subunit of the **NuA3** complex, a nucleosomal acetyltransferase of histone H3 involved in chromatin-based gene regulation. Sas3 is also required for NuA3 integrity and mediates interaction with the FACT subunit **Spt16**. (pqac-00000000, pqac-00000016, pqac-00000026) | Early purification identified Sas3 by peptide sequencing in a ~0.4–0.5 MDa NuA3 complex; loss of **SAS3** abolishes NuA3 HAT activity and disrupts complex integrity. (pqac-00000006, pqac-00000015, pqac-00000017) | Yeast-specific | John et al., *Genes & Development* — https://doi.org/10.1101/gad.14.10.1196; **May 2000** (pqac-00000000, pqac-00000006, pqac-00000016) ; Lafon et al., *Oncogene* — https://doi.org/10.1038/sj.onc.1210606; **Aug 2007** (pqac-00000003, pqac-00000025) |
| Enzymatic reaction & principal histone targets | Sas3 catalyzes **acetyl-CoA-dependent lysine acetylation of histone H3**, with **H3K14** the best-supported primary physiological target and **H3K23** also reported for NuA3. (pqac-00000009, pqac-00000010, pqac-00000011) | NuA3 acetylates **H3 on nucleosomal substrates**; early work also found it can acetylate **H4 on free histones**. Recombinant Sas3 acetylates free histones, whereas NuA3 subunits promote nucleosome engagement. H3K14 targeting is enhanced by Yng1 recognition of H3K4me3. (pqac-00000012, pqac-00000023, pqac-00000025) | Yeast-specific | Taverna et al., *Molecular Cell* — https://doi.org/10.1016/j.molcel.2006.10.026; **Dec 2006** (pqac-00000011) ; Martin et al., *Genetics* — https://doi.org/10.1534/genetics.116.199422; **Mar 2017** (pqac-00000009) ; Kim et al., *Nucleic Acids Research* — https://doi.org/10.1093/nar/gkaa781; **Oct 2020** (pqac-00000010) |
| Complex composition & reader domains | Mature NuA3 is commonly described with **Sas3, Nto1, Eaf6, Yng1, Taf14, Pdp3**; earlier biochemical work also identified **yTAFII30/TAF30** in NuA3 preparations. (pqac-00000007, pqac-00000020, pqac-00000015) | Reader modules: **Yng1 PHD** binds **H3K4me3**; **Pdp3 PWWP** binds **H3K36me3**; **Taf14 YEATS** binds acylated histone marks including **H3K9ac/crotonylation**; Taf14 ET binds EBMs in Yng1 and Sas3. (pqac-00000007, pqac-00000018, pqac-00000031, pqac-00000042) | Yeast-specific | Martin et al., *Genetics* — https://doi.org/10.1534/genetics.116.199422; **Mar 2017** (pqac-00000007, pqac-00000020) ; Nguyen et al., *Nature Communications* — https://doi.org/10.1038/s41467-024-49730-y; **Jun 2024** (pqac-00000018, pqac-00000031, pqac-00000042) |
| Localization & genome targeting | Sas3/NuA3 functions in the **nucleus on chromatin**, associating with transcribed genes and chromatinized templates; multiple studies place NuA3 over **gene bodies / mid-gene regions**, while promoter recruitment is also observed in recent Taf14-focused work. (pqac-00000022, pqac-00000028, pqac-00000029, pqac-00000027) | MNase-ChIP/ChIP analyses place Sas3 and Yng1 peaks about **750 bp** and **657 bp** downstream of the +1 dyad, respectively; genome-wide Sas3–Yng1 occupancy correlation **Spearman r = 0.48**. Recruitment depends additively on **Set1/H3K4 methylation** and **Set2/H3K36 methylation**. (pqac-00000022, pqac-00000034, pqac-00000037) | Yeast-specific | Martin preprint — https://doi.org/10.1101/096511; **Dec 2016** (pqac-00000022, pqac-00000044) ; Martin thesis-derived data — https://doi.org/10.14288/1.0364673; **Jan 2018** (pqac-00000028, pqac-00000034, pqac-00000037) ; Vicente-Muñoz et al., *FEBS Open Bio* — https://doi.org/10.1016/j.fob.2014.11.001; **Nov 2014** (pqac-00000029) |
| Pathways / biological processes | Best-supported roles are in **transcriptional regulation**, especially coupling histone acetylation to active chromatin and antagonizing Rpd3 HDAC pathways; Sas3/NuA3 also connects to **transcription elongation** via **FACT/Spt16** and has emerging links to **DNA repair** and cell-cycle/stress responses. (pqac-00000023, pqac-00000024, pqac-00000027) | NuA3 antagonizes **Rpd3S/Rpd3L** to optimize mRNA and lncRNA expression dynamics; Sas3 disruption enhances **6-azauracil** sensitivity in an Spt16-mutant background, consistent with elongation defects. (pqac-00000010, pqac-00000023) | Yeast-specific | Kim et al., *Nucleic Acids Research* — https://doi.org/10.1093/nar/gkaa781; **Oct 2020** (pqac-00000010) ; John et al., *Genes & Development* — https://doi.org/10.1101/gad.14.10.1196; **May 2000** (pqac-00000023, pqac-00000024) ; Nguyen et al., *Nature Communications* — https://doi.org/10.1038/s41467-024-49730-y; **Jun 2024** (pqac-00000027) |
| 2024 Nguyen et al. mechanistic advance | Taf14 organizes NuA3 by binding **ET-binding motifs (EBMs)** in both **Yng1** and **Sas3**, forming a dimeric ET:EBM assembly that enhances Taf14 DNA binding and is required for proper NuA3 function in transcription and genome maintenance. (pqac-00000031, pqac-00000042) | **Taf14ET–Sas3EBM Kd ≈ 18 μM** by NMR; **Taf14FL–Sas3 peptide Kd ≈ 21 μM** by tryptophan fluorescence; **Sas3 L114D** weakens binding to **~540 μM**; **V116D/I118D** abolish binding. For Yng1, **Taf14ET–Yng1EBM Kd ~0.6 μM**, **Taf14FL–Yng1EBM ~1.1–1.2 μM**. (pqac-00000032, pqac-00000033, pqac-00000038) | Yeast-specific | Nguyen et al., *Nature Communications* — https://doi.org/10.1038/s41467-024-49730-y; **Jun 2024** (pqac-00000030, pqac-00000032, pqac-00000033, pqac-00000038) |
| 2024 Nguyen et al. genomic & phenotypic data | ChIP-exo and mutant phenotyping tie Taf14–Sas3/Yng1 interactions to a restricted promoter set and stress resistance relevant to transcription/replication-repair. (pqac-00000042, pqac-00000030) | Promoter occupancy counts: **Taf14 1096**, **Yng1 71**, **Sas3 9**; **70/71** Yng1 promoters are co-bound by Taf14; **6** promoters are co-bound by all three. Mutations disrupting Taf14 binding (**Sas3 I118D**, **Yng1 I120D**) cause strong **6-AU** sensitivity and increased sensitivity to **HU** and **MMS**; Sas3 I118D shows near loss of growth and temperature-sensitive defects. (pqac-00000030, pqac-00000032, pqac-00000038) | Yeast-specific | Nguyen et al., *Nature Communications* — https://doi.org/10.1038/s41467-024-49730-y; **Jun 2024** (pqac-00000030, pqac-00000032, pqac-00000038) |
| Ortholog context (not the target protein) | Recent 2023–2024 papers also use **Sas3** for **orthologous fungal MYST HATs** in pathogens such as *Zymoseptoria tritici* and *Aspergillus fumigatus*. These studies support evolutionary conservation of a nuclear chromatin-acetylation role but are **not evidence for the specific yeast P34218 protein**. | Ortholog studies link Sas3 to virulence, cell wall integrity, and effector regulation, often with H3K14/H3K9 acetylation phenotypes, but these findings should be used only as comparative context. (pqac-00000001) | Ortholog-context | Suarez-Fernandez et al., *mBio* — https://doi.org/10.1128/mbio.01386-23; **Oct 2023** ; Wang et al., *Applied and Environmental Microbiology* — https://doi.org/10.1128/aem.01885-23; **Apr 2024** (ortholog context noted relative to yeast-specific evidence in pqac-00000001) |


*Table: This table condenses yeast-specific evidence for SAS3/P34218 function, substrates, complex organization, chromatin targeting, and 2024 mechanistic advances from Nguyen et al. It also flags ortholog-only Sas3 literature to avoid conflating non-yeast findings with the target protein.*