The POLD1/P125 protein is expressed ubiquitously across a panel of human tissues with high levels in the heart and lung tissues.
The subcellular localization of POLD1/p125 is predominantly in the nucleus and nucleoplasm.

A reduction in POLD1/p125 has been observed in senescent human skin fibroblasts and in lymphocytes from an elderly population.
POLD1/p125 expression is epigenetically regulated in response to DNA damage.
Other studies have also shown that POLD1/p125 expression is regulated by miR-155, p53 and by the long non-coding RNA, PVT1.
In the presence of DNA damage or replication stress (UV light, methyl methanesulfonate, hydroxyurea or aphidicolin), the POLD4/p12 subunit is rapidly degraded.
 The catalytic activities of p125 are different whether it is in the heterotetramer (Polδ4, with p12) or in the heterotrimer (Polδ3, without p12).
The production of the heterotrimer depends on p12 degradation by the E3 ligase RNF8, a protein involved in DSBs repair and possibly homologous recombination (HR).
In addition, the E3 ligase CRL4Cdt2 can degrade POLD4/p12 during normal DNA replication and in the presence of DNA damage.
POLD4/p12 can also be degraded by the protease µ-calpain, that is involved in calcium-triggered apoptosis.

POLD1/p125 has a NoDS domain that regulates transport to the nucleolus in response to acidosis.
 Nucleolar transport requires a direct interaction between the p50 subunit and the WRN protein.
During DNA damage response, WRN moves out of the nucleolus and thereby releases Polδ.
POLD1/p125 has also been shown to interact with PDIP46/SKAR and LMO2.
The POLD1/P125 protein is expressed ubiquitously across a panel of human tissues with high levels in the heart and lung tissues. The subcellular localization of POLD1/p125 is predominantly in the nucleus and nucleoplasm.
A reduction in POLD1/p125 has been observed in senescent human skin fibroblasts and in lymphocytes from an elderly population. POLD1/p125 expression is epigenetically regulated in response to DNA damage. Other studies have also shown that POLD1/p125 expression is regulated by miR-155, p53 and by the long non-coding RNA, PVT1. In the presence of DNA damage or replication stress (UV light, methyl methanesulfonate, hydroxyurea or aphidicolin), the POLD4/p12 subunit is rapidly degraded.  The catalytic activities of p125 are different whether it is in the heterotetramer (Polδ4, with p12) or in the heterotrimer (Polδ3, without p12). The production of the heterotrimer depends on p12 degradation by the E3 ligase RNF8, a protein involved in DSBs repair and possibly homologous recombination (HR). In addition, the E3 ligase CRL4Cdt2 can degrade POLD4/p12 during normal DNA replication and in the presence of DNA damage. POLD4/p12 can also be degraded by the protease µ-calpain, that is involved in calcium-triggered apoptosis.
POLD1/p125 has a NoDS domain that regulates transport to the nucleolus in response to acidosis.  Nucleolar transport requires a direct interaction between the p50 subunit and the WRN protein. During DNA damage response, WRN moves out of the nucleolus and thereby releases Polδ. POLD1/p125 has also been shown to interact with PDIP46/SKAR and LMO2.
POLD1