# Zinc finger protein 229

Zinc finger protein 229 is a protein that in humans is encoded by the ZNF229 gene. The ZNF229 gene is involved in regulating transcription as it can bind to DNA, either inhibiting or promoting transcription.

## Gene

This gene is located on chromosome 19 (19p13.31) spanning 22,219 base pairs on the minus strand of DNA. There are 6 exons in total.

## RNA

The longest isoform (transcript variant 1) of the ZNF229 gene has an mRNA transcript length of 4,956 nucleotides, which encode 7 exons. There is one other isoform, transcription variant 2, which differs in the 5’ UTR region and at the end of exon 5. This isoform has 4,832 nucleotides and is slightly shorter than isoform 1.

## Protein

Transcription variant 1 of ZNF229 encodes a protein that is 825 amino acids in length. Isoform 2 of ZNF229 encodes a protein made up of 819 amino acids that does not include the last 6 amino acids of exon 5 that are observed in isoform 1. The molecular weight is approximately 93 kDa and the isoelectric point is 8.88 pH. The zinc finger protein 229 has a Kruppel-associated box domain (KRAB) at the N-terminus and 17 C2H2 domains (20 amino acids long) at the C-terminus. The KRAB domain is important for transcription repression of ZNF229. In the C2H2 zinc finger domains, there are two cysteines at the beginning and two histidines at the end that allow the protein to bind to the metal zinc ion. This bond with zinc stabilizes the protein's secondary structure as they form two beta sheets and an alpha helix. As observed in other zinc fingers, the alpha helix can then bind to DNA in the major groove, allowing the protein to regulate transcription.

## Gene level regulation

The ZNF229 gene is mainly expressed in the thyroid, ovaries, and brain in adult humans. ZNF229 is ubiquitously expressed in human fetal development.

## Protein level regulation

ZNF229 does not have a transmembrane domain or signal sequence. Most zinc fingers are found in the nucleus, but ZNF229 was found to be in vesicles of human cells in one antibody study. There are other cases of zinc fingers being found outside the nucleus like ZFP36 and TNFAIP3.

## Paralogs

The Zinc Finger Protein family is large and the human ZNF229 protein has many paralogs. These are 5 paralogs of ZNF229 that range in identity from 46-52%.
| Paralogs | Identity | Similarity | Accession # | Sequence length (aa) | Chromosome location |
| ZNF229 | 100% | 100% | NP_055333.3 | 845 | 19q13.31 (44426254..44448578) |
| ZNF658 | 52% | 68% | NP_001304845.1 | 1059 | 9q21.11 |
| ZNF208 | 49% | 64% | KAI2590044.1 | 1167 | 19p12 |
| ZNF227 | 49% | 62% | NP_001276102.1 | 771 | 19q13.31 (44207547..44237268) |
| ZNF836 | 44% | 58% | NP_001096127.1 | 936 | 19q13.41 |
| ZNF112 | 46% | 57% | NP_001335210.1 | 930 | 19q13.31 (44326553..44367217) |

## Orthologs

There are orthologs of the ZNF229 human gene found in nearly all life forms. Some ortholog groups include mammals (identity of 45%), reptiles (42-46%), birds (52-56%), fish (47-54%), invertebrates (39-54%), fungi (46-55%), plants (31-39%), and bacteria (34-51%). ZNF229 did not have any significant orthologs in archaea.

## Interacting Proteins

The TRIM28 protein is predicted to bind to ZNF229 based an affinity capture-MS experiment; this is logical as TRIM28 binds to the KRAB domain, which ZNF229 contains, and acts as a corepressor.

## Clinical Significance

From GEO Profiles, a study that examined gene expression in estrogen receptor alpha-silenced MCF7 breast cancer cell lines and normal MCF7 cell line found that ZNF229 was expressed at low levels. There is a predicted transcription factor, SREBF2, found upstream of the ZNF229 gene where estrogen regulates the expression of this transcription factor.